Homeland Security Secretary Tom Ridge on Wednesday praised preparations for the upcoming Democratic National Convention, telling reporters after a tour of the site that the security apparatus for the gathering is "very, very strong."

Ridge was briefed by a host of government agencies charged with securing the convention, which begins July 26. In an afternoon news conference on the Boston waterfront, he lauded "the immense resources and the meticulous preparations that have been put in place to ensure the safety of the citizens of Boston and the well-being of all convention participants."

About 35,000 Democratic delegates, members of the media and other guests are expected in Boston for the four-day gathering. Preparations for what will be the first national political convention since the Sept. 11, 2001, terrorist attacks include unprecedented security precautions such as closing a large section of highway and one of the city's two major rail hubs because of their proximity to FleetCenter, where the convention will be held.

Ridge, who as governor of Pennsylvania was host of the 2000 Republican National Convention in Philadelphia, acknowledged that "there's going to be some inconvenience" for locals, but said it would be outweighed by "the rewards and the positive impact on your community."

With police and Coast Guard boats bobbing behind him, and FleetCenter visible across the mouth of the Charles River, Ridge repeated the warning officials have issued over the past few months that "credible reporting . . . indicates al Qaeda is moving forward with plans to carry out a large-scale attack on the United States in an effort to disrupt" the November elections.

He said that no specific threats had been made against the political convention here, or next month's Republican gathering in New York, but rejected suggestions that his election year warnings were politically motivated. "We don't do politics at Homeland Security," he said.

As part of the security precautions, area hospitals earlier this week received shipments of "chempacks" from the Centers for Disease Control and Prevention that contain treatments for chemical or biological agents that could be used in a terrorist attack. "They give us additional resources in the event of a major incident," said Rich Serino, head of Boston's Emergency Medical Services. He would not disclose the contents of the kits or what kinds of agents they are designed to protect against.

After arriving in Boston on Wednesday morning, Ridge was taken to what officials called an "undisclosed location in the Boston area" where convention security will be coordinated. He and Mayor Thomas M. Menino (D) received a private 90-minute briefing. Menino thanked Ridge for his agency's help in preparing for the convention.

Later, security officials showed off mobile command vehicles that will be used to coordinate responses to any emergency that occurs during the convention, including a $600,000 van operated by the Massachusetts Emergency Management Agency that is equipped with enough power to run on its own for seven days.

Federal Protective Service officials will monitor 75 wireless cameras stationed around the city that can zoom in on faces and license plates and beam the images to handheld devices carried by agents in the street, officials said.

Homeland Security Secretary Tom Ridge, with Boston Mayor Thomas M. Menino, right, watches a demonstration of a bomb disposal robot during his review of security for the Democratic convention.