Pat Dollard | Young Americans

WASHINGTON (CNN) — There is deep concern about the possibility of a terrorist attack in the United States this year because al Qaeda may be recruiting and giving explosives training to Europeans, many of whom can enter the country without a visa, the director of national intelligence told Congress.

On Tuesday, Mike McConnell told the Senate Judiciary Committee the greatest threat comes from al Qaeda. The terrorist organization could be training operatives to move explosives available on the commercial market from Pakistan’s tribal region through Europe and into the United States, he said.

“Europeans in large part do not require a visa to come into this country, so purposefully recruiting an operative from Europe gives them an extra edge into getting an operative or two or three into the country with the ability to carry out an attack that might be reminiscent of 9/11,” McConnell said.

His comments echo statements of other senior government officials, including Homeland Security Secretary Michael Chertoff.

Chertoff has repeatedly expressed concern that terrorists could take advantage of the visa waiver program, which allows most Europeans to travel to the United States without applying for a visa.

On Tuesday, McConnell said he also is concerned the appearance of Osama bin Laden on a recent videotape — after the terrorist leader’s lengthy absence — might be a move designed to trigger an attack.

“Our concern is that’s a signal,” McConnell said. But he added he does not view that as being as significant as the al Qaeda plan to use Europeans inside the United States.

The director of national intelligence — who oversees the CIA, the National Security Agency and all other intelligence units — made the comments in his fourth appearance before a congressional committee in the past two weeks.

Congress is again wrestling with how to renew the Foreign Intelligence Surveillance Act. Before its summer recess, Congress approved the Protect America Act, which allows the government to intercept, without a warrant, phone calls and e-mails from people outside the United States who are contacting individuals inside the country.

While supporters of the new law say it protects America from terrorists, critics say the law harms Americans’ right to privacy.

The intensely partisan atmosphere over the issue that prevailed in August was not in evidence Tuesday, as McConnell and Democratic critics of the law both expressed a willingness to compromise.

“I think if we are thoughtful about going about this the way the admiral [McConnell] has suggested, we will find a lot of the disagreement and concern and anxiety — and in some cases anger and frustration — that emerged in the August stampede can be easily worked through,” said Democratic Sen. Sheldon Whitehouse of Rhode Island.

McConnell nodded in agreement