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Senate Democrats are making last-minute changes to the hearing schedule for a soon-to-be released immigration overhaul, in an apparent bid to address Republican complaints that they're not being given enough time to review the major legislation.

The bipartisan "Gang of Eight" -- which for months has been working on the bill -- planned to unveil the legislation Tuesday, but has delayed the roll-out due to the Boston bombing tragedy. Members of that group, including Republican Sen. Marco Rubio, R-Fla., have over the past several days adamantly defended the provisions of the package, trying to counter conservative skepticism that the plan amounts to "amnesty."

At the same time, Republicans have complained that Senate leaders were not allowing nearly enough time to debate the bill, with just one hearing scheduled by Senate Judiciary Committee Chairman Patrick Leahy, D-Vt.

On Monday, Leahy made a gesture to those critics, delaying a previously scheduled hearing from Wednesday to Friday, and scheduling one more for next Monday.

"Over the course of the next week, the Senate Judiciary Committee will hold two hearings on a forthcoming, bipartisan proposal to reform the Nation's broken immigration system," Leahy said in a statement. "I look forward to reviewing the bill, holding prompt hearings on the legislation, and proceeding to debating and marking up legislation on this important issue."

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    Supporters of the bill are trying to navigate tricky political waters that have drowned prior attempts to pass an immigration overhaul. Even debates over process have the potential to scuttle a deal.

    Prominent critics include Sen. Charles Grassley, R-Iowa, the top Republican on the Judiciary Committee, and Sen. Jeff Sessions, R-Ala., the top Republican on the Senate Budget Committee. Both have raised concerns about the cost of providing a pathway to citizenship for illegal immigrants -- though Rubio's office has said it's too early to make assumptions about those costs.

    Sessions was dubious about the hearing announcement Monday.

    "Chairman Leahy's decision to now hold two hearings in two days -- on one Friday, one on Monday -- is only further proof of the Majority's desire to rush this bill with minimum public scrutiny," he said in a statement. "We are talking about legislation that will impact virtually every aspect of our society, reshape our entire immigration system, introduce at least 30 million new foreign workers into the economy, and directly impact every single American worker and taxpayer. ... Something is truly broken in Washington when the people, the law enforcement officers who protect them, and the people's representatives, have less time to review the bill than the special interests who helped write it."

    Rubio has also tried to extract more hearings out of Leahy, though he applauded the announcement Monday.

    "The Judiciary Committee's announcement that it will hold multiple hearings on the immigration bill is an encouraging development, and I will continue working with my Senate colleagues to schedule more hearings on this important legislation," he said.

    The hearing Friday will feature Homeland Security Secretary Janet Napolitano.

    Leahy said he's working with Grassley to determine who will testify on Monday.

    The bill is expected to include a host of provisions. Aside from creating a pathway to legal status for illegal immigrants, it would establish a regulated temporary worker program, make changes to border security and make changes to the legal immigration system.

    Rubio told "Fox News Sunday" that anybody living illegally in the United States and attempting to get a visa would face a long list of qualifications, which includes paying taxes, a fine and an application fee as well as having a job and waiting for at least 10 years.

    "That is not amnesty," said Rubio, a Cuban-American considered a key member of the so-called bipartisan Gang of Eight. "Amnesty is the forgiveness of something."

    The Rubio-backed plan faces scrutiny not only from fellow conservative senators but also the National ICE Council, the union representing thousands of U.S. Immigration and Customs Enforcement employees. The group has urged Rubio to exit the talks, complaining that negotiators and the White House have not involved them in drafting the bill -- though they would be expected to carry out enforcement.