WASHINGTON (CNN) -- Attorney General Michael Mukasey on Friday pressed Congress to pass an update to the Foreign Intelligence Surveillance Act, saying its delayed passage makes it harder to track terrorist suspects "by the day."
President Bush secretly instituted the National Security Agency's domestic spying program after 9/11.
The bill contains a controversial measure that grants legal immunity to telecommunications companies that cooperated with a warrantless wiretapping program that President Bush acknowledged in 2005.
Critics say the program violated the law, and phone and Internet companies now face as many as 40 lawsuits related to their participation.
Because the question of whether telecommunications companies will get the immunity "is up for grabs," Mukasey said, they are "more and more uncertain, more and more hesitant to cooperate."
"So, my answer to mom and pop is we're trying to keep you safe, but it's getting increasingly difficult," he said.
The attorney general's comments come a day after Democrats and Republicans traded verbal volleys over the fate of the bill.
Republicans complained Thursday that the House's Democratic leadership left the country vulnerable to terrorists when they failed to bring up a Senate-passed bill -- supported by Bush -- before a temporary law governing a warrantless wiretapping program expired over the weekend.
The immunity effort has held up final passage of the bill. Critics say the administration's insistence on protecting those companies from liability amounts to a "get out of jail free" card.
The Senate bill gives immunity to these companies for past activities; the House bill does not.
Both the House and Senate versions of the bill would modernize FISA by allowing U.S. intelligence to tap into phone and Internet traffic overseas without obtaining a judge's warrant, even if the calls were routed through communications centers in the United States.
"If the vote were held today, it would pass, by our count, because there are a majority of House members who support it," Mukasey said.
Democrats argue that the 1978 FISA law gives the government all the authority it needs to carry out the surveillance it seeks, and that passage of the final bill can wait until the House and the Senate reconcile their differences.
With the lawmakers out of town, Democratic staffers from key congressional committees met on Capitol Hill on Thursday afternoon to try to bridge the differences in the House and Senate versions.
Since the temporary law, the Protect America Act, expired at midnight Saturday, Republican staff members have circulated editorials and video clips critical of the House Democratic leaders' decision not to bring up the Senate bill.
Democratic aides have responded by sending out fact sheets and articles arguing that the government has all the authority it needs to continue the program while the bills are reconciled. E-mail to a friend
CNN's Deirdre Walsh and Brianna Keilar contributed to this report.