WASHINGTON – Congress is likely to postpone consideration of an immigration overhaul until the end of the year, if not longer, even as advocates are preparing for an all-out urgent push this fall to win their long-standing goal of a path to citizenship for millions of immigrants living in the country illegally.

In Washington, the sudden debate over military action in Syria and a looming faceoff with President Obama over the budget and the nation's borrowing limit have shot to the top of the legislative agenda, while Republican angst about losing Hispanic voters in the 2012 presidential campaign has faded.

In the House, where many Republicans view an overhaul bill passed by the Senate as a federal juggernaut that is too kind to immigrant lawbreakers, the legislative summer recess has done little to stoke enthusiasm for immediate action. Senior GOP aides in the House say immigration is at the back of the line, and unlikely to come up for months.

The prospect of a delay is generating frustration among supporters, who felt emboldened by a summer in which conservative opposition in House ­districts largely fizzled and immigrant groups seized the chance to lobby lawmakers on their home turf.

"We believe they can walk and chew gum at the same time," said Eliseo Medina, who leads the immigration campaign for the Service Employees International Union, referring to members of Congress. "The more they delay, the worse it will be for them."

August lobbying

Immigration groups organized hundreds of visits throughout August to congressional offices, town hall meetings, vigils, marches and rallies, creating a constant buzz in the districts of many House lawmakers, particularly Republicans. On Wednesday, advocates delivered 600,000 petitions to the West Chester, Ohio, offices of House Speaker John Boehner the old-fashioned way, in dozens of stacks of signed papers. On Sunday, Catholic priests around the country preached for a comprehensive immigration overhaul.

At a mass devoted to immigration in Cincinnati, a mix of Catholics, including immigrants from Mexico and Central America and African-Americans, prayed for Congress to act.

"Families in our communities are being ripped apart by deportations, and the system is in chaos," said Tony Stieritz, director of Catholic Social Action for the Cincinnati archdiocese, who helped organize the mass. "A vote for delay is a vote for crisis and disorder in the current system."

Jos Cabrera, 18, a high school senior from Mexico who spoke at the mass, said immigrant groups in Ohio expected to see legislation this year, adding that he and other students compared their activities to the civil rights march on Washington, recently celebrated on its 50th anniversary.

"We know this is the year," said Cabrera, who came here illegally when he was 4 and was recently granted a deportation deferral by the Obama administration. "I have put as much effort in as I can and even more. If they just keep pushing it back and back, a lot of activists will be very frustrated."

Anger intensifies

The gulf between the expectations of advocates and the reality they face in Washington is widening every day. As they feel momentum slipping away, their anger is likely to intensify this fall.

And time is not on their side. In June, the Senate passed a bipartisan plan to overhaul border security and grant illegal immigrants a chance to earn citizenship. If the House does not take up the immigration issue until 2014, members will face the prospect of voting on a highly contentious issue in the middle of a congressional election year.

Republican primaries begin in the spring of 2014, and many lawmakers may be reluctant to overhaul the immigration system just before facing their conservative constituents. If Congress does not complete action in early 2014, congressional aides said the issue could be delayed until after the elections in November 2014.

But leaders of groups supporting an immigration changes say they do not plan to let up. The organizations plan rallies in at least 40 cities on Oct. 5 followed by a march and rally in Washington on Oct. 8.