WASHINGTON – Homeland Security Secretary Chertoff announced sweeping reforms at his two-year-old department yesterday, pledging to make mass transit safer from terror attacks as part of a new focus on the nation’s greatest vulnerabilities.

The overhaul at the Homeland Security Department has been planned for months but comes on the heels of last week’s bombings of London’s subways and bus systems. It also includes plans to centralize the department’s terror analysis, puts a higher priority on bioterrorism issues, and tightens American borders against illegal immigrants.

The changes aim to address turf wars and growing pains at the sluggish bureaucracy that was created by combining 22 federal agencies in 2002 – in direct response to the September 11, 2001, terror attacks.

Mr. Chertoff said Homeland Security is “open to change.”

“We will be straightforward,” Mr. Chertoff told a packed ballroom of hundreds of lawmakers, department employees, and other officials. “If something goes wrong, we will not only acknowledge it, we will be the first to fix the error.”

But, he added, “we will also stand up and let people know when we’ve done things the right way or see a better way ahead.”

Mr. Chertoff opened the speech with condolences to the British people after the London bombings. He said Homeland Security would look to deploy technology to detect explosives and bioterror, chemical, or radioactive material on the nation’s rail, subway, and bus systems.

Homeland Security Deputy Secretary Michael Jackson later told reporters the detection tools would probably be installed in large metropolitan areas with subway systems that face the greatest risk of attack, like New York and Washington.

Those detection technologies, which are still in varying stages of development, could cost the government an estimated $6 billion to buy, install, and maintain in mass transit, said American Public Transportation Association president William Millar. He agreed with the push for better weapons detectors, as long as federal funding is provided and “it doesn’t hold up our passengers.”

An estimated 32 million commuters ride subways, trains, and buses every day, Mr. Millar said.

On analyzing terror intelligence – a chief reason for creating the department – Mr. Chertoff said he would name a director to centralize information gathered by 11 Homeland Security bureaus.

The director, who has not yet been appointed, will be asked to improve the department’s standing within the intelligence community, where it is perceived as a junior partner and often left out of the loop.

Mr. Chertoff also said he would create a chief medical officer to oversee bioterror policy and coordinate responses to biological attacks. Poor information flow between federal agencies during the Washington area’s false anthrax scare this year contributed to the decision to create the post.

In welcome news to Washington-area passengers, the department also will lift a rule that had forbidden passengers from leaving their seats for 30 minutes before flying into or out of Reagan National Airport.

As another top priority, Homeland Security will seek to tighten American borders against potential terrorists or criminals, but Mr. Chertoff said doing so should not come at the cost of immigrants entering the country to find work.

He said he and Secretary of State Rice will soon announce plans to ease visa hassles for foreigners entering the country to visit, work, and study.

Of the proposed changes, 80% can be accomplished under Mr. Chertoff’s existing authority; the remainder require congressional approval.