WASHINGTON (Reuters) - President George W. Bush, marking five years since the Department of Homeland Security was created, said the United States was not safe from terrorists who were plotting another attack as he spoke.

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Bush, who is battling Democrats in the U.S. House of Representatives over eavesdropping legislation, has been accused over the years by critics of using scare tactics for political advantage.

In a speech before Homeland Security Department employees, Bush said it was important that Americans remember “some serious lessons on September the 11th,” and that U.S. security agencies must take the words of al Qaeda leader Osama bin Laden “very seriously” when he says operations are in preparation.

“At this moment, somewhere in the world, a terrorist is planning an attack on us. I know that’s inconvenient thought for some, but it is the truth,” Bush said.

Bush and House Democratic leaders have locked horns over legislation that would grant immunity from lawsuits to private firms that helped the United States monitor communications of terrorism suspects in the aftermath of the September 11 attacks.

The Senate passed legislation including the blanket, retroactive immunity that Bush wants, but House Democratic leaders have not brought that bill for a vote.

House Democrats have sought more information about the activities already undertaken by telephone companies at the request of the Bush administration.

Many Democrats in Congress argue the courts should decide whether companies violated the law, instead of Congress shielding them from potentially billions of dollars in civil damages from lawsuits.

“We are still working very hard to see if we can come to agreement,” said House Speaker Nancy Pelosi, a California Democrat. “But we’re not going to abandon the Constitution of the United States.”

She said Bush has authorities needed under current laws.

Bush is pressing the House to approve the Senate bill and get it to him by Saturday to sign into law.

He said U.S. spy agencies cannot eavesdrop on terrorism suspects without the help of private companies.

“To stop new attacks on America we need to know who the terrorists are talking to, what they’re saying, and what they’re planning,” he said. “We cannot get this vital information without the cooperation of private companies.”