WASHINGTON – Two U.S. B-52 bombers flew a show-of-force mission in the Persian Gulf on Thursday that military officials said was intended to deter Iran and its proxies from carrying out attacks against American troops in the Middle East amid rising tensions between the two countries.

The lumbering warplanes' 36-hour round-trip mission from Barksdale Air Force Base in Louisiana was the second time in three weeks that Air Force bombers had conducted long-range flights near Iranian airspace on short notice. The United States periodically conducts such quick demonstration missions to the Middle East and Asia to underscore U.S. air power to allies and adversaries, but the two missions within a month is unusual.

The multinational mission, which included aircraft from Saudi Arabia, Qatar and Bahrain, was routed well outside Iranian airspace. The U.S. warplanes were in the broader Gulf region for about two hours before returning home, officials said. Two other B-52s from Minot Air Force Base in North Dakota conducted the same type of long-range mission in the area Nov. 21.

The flight Thursday comes on the heels of the assassination last month of Iran's top nuclear scientist, an attack Iran has blamed on Israel with possible U.S. complicity. The bomber missions also come just weeks before the anniversary of the U.S. drone strike in January that killed a senior Iranian commander, Gen. Qassem Soleimani, in Iraq.

Iran has vowed to avenge both deaths.

"Potential adversaries should understand that no nation on earth is more ready and capable of rapidly deploying additional combat power in the face of any aggression," Gen. Kenneth McKenzie Jr., head of the military's Central Command, said in a statement Thursday.

"We do not seek conflict," he said, "but we must remain postured and committed to respond to any contingency."

Military officials declined to say what live munitions, if any, the aircraft carried on their recent missions, but in recent years the hulking bombers have conducted strikes with laser-guided conventional bombs against insurgent targets in Afghanistan.

Even as American officials sought to cast the flights as defensive in nature, President Donald Trump's top national security advisers had days earlier dissuaded him — at least for now — from considering bombing Iran's main nuclear site in the coming weeks.

Given that White House officials have discussed aggressive options, Middle East specialists said it is little wonder that Iran may have difficulty deciphering the Trump administration's intentions, especially during a volatile period in which Trump continues to insist falsely that he defeated President-elect Joe Biden.

In a briefing with a small group of reporters before the mission Thursday, a senior military official said American intelligence analysts had detected "planning going on" — including preparations for possible rocket strikes or worse — by Iran and Shia militias in Iraq that it supports.

Over the past year, Iranian-aligned proxies in Iraq have conducted more than 50 rocket attacks on bases where American troops are housed, as well as on the U.S. Embassy in Baghdad, and launched 90 attacks on convoys carrying supplies to U.S. troops, according to the Pentagon.

"In short, Iran is using Iraq as its proxy battleground against the United States, with Iran's ultimate objective being to eject the United States and our forces from Iraq and the broader Middle East," Mc­Kenzie said last month during a virtual conference on the Middle East.