Hershey, Pa. ? President Bush gave an impassioned defense Monday of the Patriot Act, using a visit to this electoral battleground state to warn that if the law begins to expire as scheduled in 20 months it would undermine domestic security.

“It’s a law that is making America safer,” Bush said of the measure that expanded the government’s surveillance and detention powers — and has been widely criticized by both liberals and conservatives.

With chief political adviser Karl Rove in tow, Bush made his 27th trip to Pennsylvania, a state he lost in 2000 and one he has visited the most since taking office. State polls show Bush with a slight lead over Democratic rival John Kerry in the fight for Pennsylvania’s 21 electoral votes.

The purpose of the trip was twofold as Bush, for the first time this year, was raising cash for another candidate — four-term Republican Sen. Arlen Specter, who is trying to fend off a primary challenge from conservative GOP Rep. Pat Toomey.

Bush’s message on the Patriot Act didn’t mesh with Specter, who is among 18 co-sponsors of legislation that would amend the law.

Key provisions of the Patriot Act aren’t set to expire until the end of 2005, but Bush argued that the law is critical for keeping tabs on terrorists and should be renewed. He mentioned the Sept. 11, 2001, crash of a hijacked airliner 140 miles away in Shanksville.

“The terrorists declared war on the United States of America and the Congress must give law enforcement all the tools necessary to protect the American people,” Bush said in his call for Congress to make the law’s provisions permanent.

Congress approved the Patriot Act after the 9-11 attacks, but liberals and conservatives in Congress want to allow some of the act’s provisions to expire and have introduced several bills to do so. They argue that parts of the law are too intrusive on Americans’ lives.

Opposition to the law has forced lawmakers to pass resolutions against it in Alaska, Hawaii, Vermont and Maine, according to the American Civil Liberties Union. The ACLU says more than 291 communities representing nearly 50 million people in 39 states have supported resolutions assailing the law. The Lawrence, Kan., City Commission will consider such a resolution tonight.

Bush did not explain why he felt compelled to promote the law’s permanence 20 months before it begins to expire, but his speech came as his administration has been under fire for the steps it took before the 9-11 attacks with the intelligence it had. The independent commission investigating the attacks has kept the matter in the spotlight for weeks, putting Bush on the defensive on an issue his campaign regards as a political strong suit.

Today, the president will speak about the Patriot Act with law-enforcement officers in Buffalo, N.Y., near the site of recent criminal cases against the Lackawanna Six, a group of Yemeni-Americans convicted of supporting terrorism by briefly attending al-Qaida camps in Afghanistan.

Kerry voted for the Patriot Act, but campaign spokesman Phil Singer said Bush was trying to “mislead America into thinking that his policies have solved the intelligence problems exposed by the 9-11 attacks.”

“If he really wants to improve intelligence, the president should follow John Kerry’s lead and focus on improving the Patriot Act to make sure that the agencies charged with protecting our security are talking to one another and have the resources they need,” Singer said. “Simply playing election-year politics with the Patriot Act won’t accomplish that goal.”