WASHINGTON (AP) – Answering criticism about security gaps at U.S. seaports, the Bush administration said Tuesday it will conduct background checks on an estimated 400,000 port workers to ensure they do not pose a terrorist threat.

Names of employees who work in the most sensitive areas of ports will be matched against government terror watch lists and immigration databases, Homeland Security Secretary Michael Chertoff said. Additionally, the Homeland Security Department will issue tamper-free identification cards to roughly 750,000 workers _ including truckers and rail employees _ who have unrestricted access to ports.

The added scrutiny, however, will not immediately include a criminal background check for workers, although Chertoff said that might happen in the future. The Transportation Security Administration _ and not the FBI _ will conduct the background checks, he said.

“We may expand the number of databases,” Chertoff said. “Our first step is to do terrorists watch lists and immigration status.”

The new safeguards are part of what Chertoff called a “ring of security” around U.S. ports.

“We’re going to focus on those who could potentially be the greatest risk to our security,” he said at a news conference in Washington.

The Bush administration has been under fire for months about what critics call gaping holes in security measures at ports, which were highlighted after a Dubai company’s purchase of a British firm gave it control of six American ports. An outcry in the Congress led the Dubai company, DP World, to decide to sell the U.S. operations to an American firm.