WASHINGTON — Mayor Bloomberg is stepping up his effort to secure more federal funding to help employees sickened by the toxins at ground zero, telling Congress and the Bush administration that the country’s debt to New York has not been paid.

The mayor testified before a Senate panel prior to meeting with the secretary of Health and Human Services, Michael Leavitt, and then with the new House speaker, Rep. Nancy Pelosi. The city is seeking about $1 billion to fund treatment and monitoring programs, along with the reopening of the World Trade Center Victim Compensation Fund to hasten the settlement of thousands of lawsuits that the city’s Law Department is now fighting in court. Mr. Bloomberg also asked that another $1 billion allocated for insurance purposes be transferred into the fund.

“Congress cannot turn its back on those who responded with courage and suffered through this terrible catastrophe,” he said at a hearing led by Senator Kennedy of Massachusetts. Repeating what has become a refrain in his frequent trips to request more federal dollars, he added: “After all, 9/11 was not just a strike against New York — or Washington. It was an attack against all of America.”

City officials say current funding for key programs will soon run out, leading to an aggressive push by the city’s congressional delegation to get the ear of the new Democrat-led Congress and the Bush administration. Senator Clinton helped organize yesterday’s hearing in the Health, Education, Labor, and Pensions Committee, and she is planning to convene another panel on her own next month focusing on the lingering environmental effects of the September 11, 2001, attacks. City officials testified at a House hearing a few weeks ago, and several more are expected.

Mr. Bloomberg sounded an even louder alarm yesterday, saying the city could stand to lose billions of dollars in litigation and adding that there are questions as to whether a current $350 million cap on liability would stand up in court.

The two Republicans at the hearing, Senators Enzi of Wyoming and Coburn of Oklahoma, expressed sympathy for the city’s cause, but they acknowledged that officials were asking for, in the words of Mr. Enzi, “quite a bit of money.”

Mr. Coburn suggested that instead of the yearly appropriation of $150 million that the city is seeking, the government should create a permanent endowment to cover health costs for ground zero workers. Mr. Bloomberg indicated that he was open to the possibility.

While many Democrats on the city’s congressional delegation have criticized the Bush administration for dragging its feet in setting up a federal health program, Mr. Bloomberg was more diplomatic. “We’re not into politics,” he told reporters before meeting with Mr. Leavitt.