The prime minister of Ireland today is appearing before a joint session of Congress to make a plea on behalf of illegal Irish immigrants after disclosing that he has spent the past several months wrangling with individual members for a special visa deal.

The taoiseach, Bertie Ahern, said his administration has been holding “detailed” conversations with the Bush administration and lawmakers, including senators Schumer and Kennedy, about the possibility of increasing the number of visas for Irish immigrants.

The prime minister is addressing Congress at a moment when he is on the defensive with the Irish community in America, where many immigrants impatient for a deal have accused him of slacking off on their cause.

Irish immigrant groups have been pushing for a bill that would create a new set of visas available only to the Irish, including those living in America illegally, ever since a bill that would have created a path to legalization for illegal immigrants of all nationalities collapsed last summer.

With significant political clout thanks to the well-established Irish-American community and a relatively small request — the number of Irish coming to America has dwindled in recent years as Ireland’s economy has expanded — the groups are hopeful lawmakers will be sympathetic to their cause.

In an op-ed published this month in the Irish Voice, a newspaper published for Irish living abroad, Mr. Ahern sought to assuage concerns that he is not fighting for the immigration pact.

“Over many years, we have engaged intensely with the U.S. administration and with Congress to try to find a solution for our citizens caught in such unfortunate circumstances,” he wrote, adding that in the past few months, “the matter has been a lead item on my agenda.”

The strategy has created frictions in America’s Irish community. Some Irish leaders have argued that the Irish shouldn’t abandon other groups for their own gain, and should be using their political influence to bring everyone along with them.

Among other immigrant groups, reaction to the efforts by the Irish to get their own deal has been more muted than the heated disputes within the Irish community itself.

The director of the Northern Manhattan Coalition for Immigrant Rights, Raquel Batista, said the Irish efforts could be comparable to those of Central Americans or Haitians who have tried to gain refugee status or to extend temporary legal status periods after natural disasters in their countries.

“All the immigrant groups tried to do something together, and it didn’t work,” she said, but added: “I hope that when it comes down to it, that folks like Charles Schumer and Hillary Clinton really commit to passing immigration reform that will benefit more than one group and community.”

The Irish community has been further divided over a comment Mr. Ahern made during a recent visit, when he suggested an amnesty for immigrants would be unrealistic. He attempted to soften this idea in his op-ed.

Irish leaders have attacked the comment and have also accused the prime minister of secretly working on an immigration deal that would not include illegal immigrants.

“We know it is a difficult lift, but unlike the government we are definitely not prepared to give up the fight,” an op-ed in the Irish Voice attributed to one of the lead Irish immigrant organizations, the Irish Lobby for Immigration Reform, said.

The lobby group said it has also been meeting with “senior politicians,” including one “senior senator,” to talk about a deal.

Representatives for Messrs. Kennedy and Schumer did not respond to repeated requests for comment yesterday about the discussions.

It is unlikely that any deal would be worked out in the short term, as the country focuses on the presidential campaign. Also, Mr. Ahern is stepping down from his position as soon as next month in the wake of a corruption investigation, although his successor, Brian Cowen, is expected to be an even stronger advocate for the immigration deal.

Many Irish are hopeful that the conclusion of the election could bring about the speedy negotiation of a pact, particularly if either senators McCain or Clinton — who have been supportive of the Irish in the past — are elected.

According to one community leader, Brian O’Dwyer, the chairman of the Emerald Isle Immigration Center, many in the Irish community have written off Senator Obama — despite his Irish heritage — as being opposed to any immigrant deal that would single out only Irish immigrants.

“I think we just have to wait for a new president and a new Congress,” Mr. O’Dwyer said. “Our odds are two out three that we’re going to get something done.”