House Republicans are getting pressure from a key Senate Republican and others as they get ready to tackle legislation aimed at overhauling the nation’s immigration system.

Alabama Sen. Jeff Sessions, the top Republican on the Senate Budget Committee, delivered a 30-page package to all 232 House Republicans on Wednesday that offers a point-by-point rebuttal to the expected immigration guidelines that House Speaker John Boehner and other leaders plan to circulate this week among GOP members.

Sessions told members of his party they must “end the lawlessness – not surrender to it" – and they must defend the legitimate interests of millions of struggling American workers.

Part of the 30-page package included a memo from Sessions, an analysis from his staff on the Senate Budget and Judiciary committees and a summary of opposition from conservatives. It was delivered shortly before House Republicans left Washington for their annual retreat in Cambridge, Md.

High on the retreat's agenda is immigration, which Republican leaders hope to tackle this election year despite strong opposition from some members. The starting point is a statement of principles that is expected to focus on border and interior security, legalization for some of the 11 million immigrants living here illegally and ensuring that Obama enforces any law, according to lawmakers, congressional aides and outside advocates, speaking on condition of anonymity because they weren't authorized to publicly discuss the principles being drafted.

"We're going to outline our standards, principles of immigration reform and have a conversation with our members, and once that conversation's over we'll have a better feel for what members have in mind," Boehner told reporters this week.

Separately, several lawmakers are working on legislation dealing with children of parents in the United States illegally, visas for guest workers and legalization that would require immigrants to pay fines and back taxes.

Republicans insist that the party must pass reforms and address the issue of the 11 million immigrants living in the United States illegally to be competitive in presidential elections. In 2012, Republican presidential nominee Mitt Romney, who suggested that immigrants "self-deport," won just 27 percent of the Hispanic vote.

"It's no secret we have millions of people who are here, who are unlawful and we can't deny that and I think that's something that has to be dealt with," said Rep. Mario Diaz-Balart, R-Fla., who has been working on legislation, "but lot of components have to be dealt with."

The Senate last year passed a comprehensive, bipartisan bill that addressed border security, provided enforcement measures and offered a path to citizenship for those living here illegally. The measure stalled in the GOP-led House, where leaders want to take a more piecemeal approach.

In his memo, Sessions warned of the negative impact of the House immigration proposal on U.S. workers, taxpayers and the rule of law.

His analysis said increasing the number of immigrants would hurt an already weak economy, lower wages and increase unemployment. He cited White House adviser Gene Sperling's comment earlier this month that the economy has three people looking for every job opening.

He said the House GOP leaders' plan that's taking shape would grant work permits almost immediately to those here illegally, giving them a chance to compete with unemployed Americans for any job. He said it would lead to a surge in unskilled workers and would provide amnesty to a larger number of immigrants in the country illegally, giving them a chance to apply for citizenship through green cards.

"House Republicans, in crafting immigration principles, should reply to the president's immigration campaign with a simple message: Our focus is to help unemployed Americans get back to work, not to grant amnesty or to answer the whims of immigration activists and CEOs," Sessions said in his memo.

FoxNews.com obtained a copy of Sessions' critique.

Notably, two members of the House leadership, Boehner and Rep. Cathy McMorris Rodgers, R-Wash., spoke about dealing with the broken immigration system in their responses to Obama's State of the Union address. How rank-and-file Republicans will respond is unclear, especially with a great deal of GOP wariness about whether Obama can be trusted to enforce an immigration law.

Obama's waiver or suspension of provisions of his four-year-old health care law have increased suspicions among Republicans, and Sessions' analysis highlighted the president's State of the Union comments that he might act unilaterally on some issues if Congress balks.

Diaz-Balart expressed cautious optimism, putting the odds of House action on immigration at 30 percent, up from 5 percent earlier.

"There's a consensus that the system is broken and I'm seeing more and more a desire to fix it," he said in an interview. "Speaker Boehner has been very clear, leadership has been very clear. We're going to do it methodically, that we're going to look at it case by case, step by step, we're not going to rush it."

The Associated Press contributed to this report.