WASHINGTON -- With just a few days to go before a lengthy pre-election recess, Congress must try to tackle hugely complex and controversial pieces of legislation on terrorism, immigration and billions of dollars in federal spending, Sen. Arlen Specter said yesterday.

"I have been a senator for a while, but I have never seen so much work left to the last week," the Pennsylvania Republican said in a speech at the National Press Club, where he laid out some of the main challenges facing him and his colleagues.

The Bush administration and congressional Republicans are hoping to make significant headway on an ambitious agenda, focusing on the president's plans to monitor, detain and prosecute terrorism suspects.

Mr. Specter offered praise for a deal struck last week by Mr. Bush and three top Senate Republicans after the senators pressured to bar use of overly harsh interrogation techniques. He said it would show that the United States is committed to following the Geneva Conventions. But Mr. Specter expressed concern that the president's proposals would leave some suspects in a state of legal limbo, by preventing them from challenging their detention in court.

Earlier in the day, Mr. Specter held a Senate Judiciary Committee hearing on the U.S. Constitution's guarantee of those habeas corpus rights, and he said he couldn't support a bill that denied them.

Several prominent lawyers testified that the U.S. government has already gone too far by holding hundreds of prisoners at the U.S. military prison in Guantanamo Bay, Cuba. But other legal experts, including a former counsel for the Bush administration, argued that combatants caught on battlefields in places like Afghanistan don't have legal rights under the U.S. Constitution.

During his speech before the press club, Mr. Specter said he would try to amend the bill to address his concerns. Ultimately, he said, any new law likely will have to go before a judge for legal scrutiny. In June, the Supreme Court blocked some of the Bush administration's methods for prosecuting terrorism suspects, forcing Congress to take up the issue.

Mr. Specter's position appears to have considerable support, including the backing of 33 former diplomats and even Kenneth Starr, the special prosecutor who investigated former President Bill Clinton. They said in letters to lawmakers that the bill as written would damage the country's credibility in the war on terrorism.

The habeas corpus issue doesn't appear to be a deal-breaker for the White House. "We continue to work with the senators on this complicated legislation, and we're confident we'll be able to pull this bill across the finish line," White House spokeswoman Dana Perino said in an e-mail to the Associated Press.

Congress this week also will consider legislation regarding electronic surveillance of suspected terrorists.

The intense focus on national security issues has pushed aside debate on the future of immigration in the United States, but Mr. Specter said he still hoped that the Senate and House could come to an agreement over how to deal with the nation's millions of undocumented immigrants.

The Senate has passed a bill that would create a guest-worker program for those immigrants, while House Republicans have likened such a program to amnesty for lawbreakers. They prefer an emphasis on enforcement, including the building of a fence along portions of the U.S.-Mexico border.

"The House of Representatives doesn't think very much of the bicameral system," Mr. Specter said. "I'm for that fence, but I'm not for that fence piecemeal. We have a guest-worker program that the president [supports]." He has said he fears that passage of enforcement-only legislation will leave the Senate with no leverage to pressure for the guest-worker plan.

There are also several major appropriations bills before Congress, including a multibillion-dollar defense authorization bill.

Mr. Specter, in his fifth Senate term, used yesterday's speech as an opportunity to review some achievements of his first two years as chairman of the Judiciary Committee. He cited approvals for two new Supreme Court justices and a low vacancy rate among federal judges.

He also discussed a bill that would shield journalists from imprisonment when they decline to reveal their sources to prosecutors, except in cases of national security. The issue stems from when former New York Times reporter Judith Miller was sent to prison last year for refusing to disclose her sources in the Valerie Plame CIA leak case to a federal prosecutor.

Mr. Specter said that case didn't reach the standard for locking up a journalist. Many states have approved similar "shield" laws, and Mr. Specter's committee held its final hearing on the federal bill last week. He said he hoped to move it toward passage when Congress returns from its recess later this year. "We're not doing it for reporters," he said. "We're doing it for the country."

Mr. Specter also took a question on his difficult battle last year with cancer, saying he made it through that period in his life by sticking to his busy schedule of Senate business and early-morning squash matches.

"The lesson is," he said, "don't quit."