WASHINGTON — For the first time since taking office, President Obama is diving into the thorny details of the country's long-running immigration battles, summoning lawmakers to the White House this week for what aides say will be an "honest discussion of the issues" to "identify areas of agreement, and areas where we still have work to do."

The meeting is highly anticipated by Latino leaders and immigrant advocates eager for Obama to honor his campaign promise to put millions of undocumented workers on a "pathway to citizenship."

But many Democrats are concluding that they may not have the muscle to pass such a controversial measure — at least not now, and possibly not until after the 2010 mid-term elections.

And even though Obama used a Hispanic prayer breakfast Friday to reiterate his intention to pass some sort of new immigration plan during his presidency, this week's gathering demonstrates how the White House and congressional leaders are trying to strike a careful balance.

They seek to assuage Hispanic voters, who are a key constituency, while avoiding specific promises on timing and substance and trying not to antagonize independent voters who may have a skeptical view of legalization.

CHANGE IN PLAN

Obama, for example, slightly recast his citizenship plan promise during Friday's remarks, saying that new legislation should "clarify the status of millions who are here illegally, many who have put down roots."

"For those who wish to become citizens," he said, "we should require them to pay a penalty and pay taxes, learn English, go to the back of the line behind those who played by the rules."

The biggest obstacle to speedy passage of a citizenship plan, according to interviews with lawmakers and Capitol Hill strategists, is the House. Democrats hold a wide majority there, but at least 40 members represent moderate or conservative swing districts where legalization plans are unpopular and often derided as "amnesty" for lawbreakers.

"This is a very, very difficult issue," said Rep. Jason Altmire, a Democrat elected in 2006 from rural western Pennsylvania. "The Democratic Party is doing everything they can to capture this very fast-growing community, and I understand that. But I'm not in that camp."

The White House has downplayed expectations for this week's meeting.

According to Latino lawmakers who met with Obama this spring, the president had promised to host a summit with lawmakers and advocacy groups, just as he did with healthcare leaders when he kicked off the debate on that issue. Instead, the immigration event will be small and private and will include only House and Senate members involved in the immigration debate.

Moreover, the White House is careful to point out that Obama wants to merely begin the debate. He is not promising that a plan will be passed this year.

BROKEN PROMISE

Some Latino leaders argue that failing to pass the measure this year would violate the pledge Obama laid out last year, when he told the National Council of La Raza that he would make the issue "a top priority in my first year as president." But he was careful in that speech not to promise passage during his first year.

The gathering "is intended to launch a policy conversation, with the hope of having a substantive debate later this year," said White House spokesman Nick Shapiro. Several factors suggest that a delay is likely.

Obama already has delivered one major victory to Latino voters, two-thirds of whom backed him in last year's election. That was the nomination of Sonia Sotomayor, who would be the first Latina on the Supreme Court.

Some strategists fear that rising unemployment could make lawmakers even more reluctant to support a measure that would be portrayed by opponents as a jobs bill for illegal immigrants.