CAIRO — Organizers of a mass protest against Egyptian President Mohammed Morsi claimed Saturday that more than 22 million people have signed their petition demanding the Islamist leader step down, asserting that the tally was a reflection of how much the public has turned against his rule.

The announcement adds to a sense of foreboding on the eve of opposition-led mass demonstrations that many fear could turn deadly and quickly spin out of control, dragging the country into a dangerous round of political violence.

The demonstrations planned for Sunday reflect the growing polarization of the nation since Morsi took power, with the president and his Islamist allies in one camp and seculars, liberals, moderate Muslims and Christians on the other.

There is a sense among opponents and supporters of Morsi that Sunday's rally is a make or break day. The opposition feels empowered by the petition, known as Tamarod, or Rebel, but it offered no proof regarding the figures. If verified, it would mean that nearly double the number of people who voted for Morsi a year ago are now calling for him to step down.

"Honestly, if (Sunday) is not a game changer, we might all just pack up our bags and leave," said Mahmoud Salem, a prominent blogger known by his blog's name Sandmonkey and a vocal critic of the Muslim Brotherhood, from which Morsi hails.

While violence is likely in such a tense atmosphere, Salem said it would not play out in favor of Morsi supporters because they will be outnumbered.

"They have alienated everybody," he said. Even if no violence breaks out, Salem said civil disobedience is expected in a movement designed now to "save the country."

Morsi's supporters, on the other hand, question the petitions, saying his opponents are led by members of the ousted regime of Hosni Mubarak who are trying to orchestrate a comeback and are instigating violence.

"Today and tomorrow will be the real birth of this nation," said Hani Salaheddin, a presenter on the Muslim Brotherhood-affiliated TV station Misr 25, predicting that Sunday will bring an end to the questioning of Morsi's mandate.

"Tomorrow is the end of every corrupt person," he said, as the slogan "legitimacy (of the ballot box) is a red line," appeared on the screen.

Already, clashes across a string of cities north of Cairo over the past week have left eight people dead, including an American and a 14-year old, and hundreds injured. Clashes broke out outside offices of the Muslim Brotherhood and its party in at least five different governorates, and rival protests turned into violent confrontations.

Thousands are still taking part in rival sit-ins, in place since Friday in Tahrir Square for opponents and in an east Cairo suburb, Nasr City, for supporters of Morsi.

An Associated Press reporter saw Morsi supporters at a Cairo sit-in doing military-style fitness drills, with some wearing homemade body armor and construction helmets and carrying sticks. They said they had no intention of attacking opposition protesters, and would only act in self-defense or to protect the nearby presidential palace.

Highlighting the nervousness over Sunday's protests, President Barack Obama said the U.S. is working to ensure its embassy and diplomats in Egypt are safe after the 21-year old American was killed in Alexandria, Egypt's second largest city. He urged all parties to refrain from violence and the police and military to show appropriate restraint.

Adding to the tension, eight lawmakers from the country's interim legislature announced their resignation Saturday to protest Morsi's policies. The 270-seat chamber was elected early last year by less than 10 percent of Egypt's eligible voters, and is dominated by Islamists who support Morsi.

A legal adviser to Morsi also announced his resignation late Saturday in protest of what he said was Morsi's insult of judges in his latest speech.

With a sense of doom hanging over the country, Defense Minister Gen. Abdel-Fattah el-Sissi last Sunday gave the president and his opponents a week to reach a compromise and warned that the military would intervene to prevent the nation from entering a "dark tunnel."

Morsi had called for national reconciliation talks but offered no specifics. Opposition leaders dismissed the call as cosmetics.

Exchange of accusations was running high Saturday, in a rivalry that has increasingly been portrayed by Morsi supporters as an attack on Islamists in power.

The Tamarod youth movement claimed its petition is evidence of what it says is widespread dissatisfaction with Morsi's administration, and has used the signature drive as the focal point of its call for millions of people to take to the streets to demand the president's ouster.

Mahmoud Badr, a Tamarod leader, told reporters Saturday a total of 22,134,460 Egyptians have signed the petition. He did not say whether there had been an independent audit of the signatures.

Badr blamed Morsi supporters of dragging the peaceful movement toward violence to "terrorize" the public and avert a mass turnout in the streets.

On Tamarod's Twitter account, the movement appealed to supporters to gather in every street in their hometowns instead of converging to the main rallies planned in Tahrir square and outside Morsi's palace.

At a press conference organized by Morsi supporters late Saturday for their members killed in recent violence, organizers showed multiple videos of previous protests where violence raged, showing images of attacks on the Brotherhood offices and blaming "paid thugs" for it.

"Tamarod are thugs," the crowd chanted at the conference held at the pro-Morsi sit-in.

Assem Abdel-Maged, leader of the formerly militant Gamaa Islamiya group, told the crowd that the Tamarod campaign was a "crusader war" against Islamists, led by extremist Christians to liberate Egypt from Islam. He added that his supporters collected 26 million signatures in support of Morsi.

"The issue now is war," he said. "Sunday's march is decisive."

Morsi's supporters have long doubted the validity and authenticity of the collected signatures.

"How do we trust the petitions?" asked Brotherhood member Ahmed Seif Islam Hassan al-Banna. "Who guarantees that those who signed were not paid to sign?"

But opponents of Morsi say the petition has already served its purpose, dealing a symbolic blow to Morsi's mandate and putting in stark terms the popular frustrations with an administration that critics say has failed to effectively deal with the country's pressing problems, including tenuous security, inflation, power cuts and high unemployment.

In a statement ahead of the protests, opposition leader Mohammed ElBaradei said massive turnout is expected Sunday, calling for it to be peaceful and civilized. He called on Morsi to listen to the masses, and accept early elections.

"All of Egypt should go down tomorrow to say that we want to go back again to the ballot box," ElBaradei said in his recorded message sent to reporters. "We gave (Morsi) a driving license but he couldn't drive the car."

He added: "We all feel the country is collapsing, not because the president is from the Brotherhood ... But because the ruling system has failed completely."

On Saturday, Morsi met with the defense and interior ministers to review preparations to protect the protesters and vital state facilities during Sunday's demonstrations.

The focus of Sunday's protests is Morsi's Ittihadiya palace in Cairo. As a precaution, the president and his family are reported to have moved into the Cairo headquarters of the Republican Guard, the branch of the army tasked with protecting the president and presidential palaces.

With expectations of violence running high, the military has dispatched troops backed by armored personnel carriers to reinforce military bases on the outskirts of cities expected to be flashpoints.

In Cairo, additional forces were deployed to military facilities in the suburbs and outlying districts. Army troops are also moving to reinforce police guarding the city's prisons to prevent a repeat of the nearly half dozen jail breaks during the chaos of the 2011 uprising.

Many Egyptians fear the new round of unrest could trigger a collapse in law and order similar to the one that occurred during the 2011 revolt. Already, some residents have increased security around their homes, erecting metal fences and installing barbed wire. Residents in some of the residential compounds and neighborhoods to the west of the city are reporting gunmen showing up to demand protection money or risk being robbed.

The police have stepped up patrols on the outskirts of the city, ostensibly to prevent weapons and ammunition from coming into the city to be used in case of an outbreak of violence. The army is advertising hotlines for civilians to call if they run into trouble.