Advocates for ailing Sept. 11 first responders urged Congress on Thursday to permanently extend a law providing medical monitoring and treatment for the rescue workers, saying they need reassurance that their health care will not be cut off.

Dr. John Howard, the administrator of the World Trade Center Health Program, told members of the House Energy and Commerce Committee that extending the law would help clinicians treat victims, and allow administrators to better plan patient care. He pointed out that there are affected individuals in 429 of the 435 congressional districts.

"It's stressful to be told on a year-to-year basis that your care might be taken away," Howard said. "From the administrative perspective, it's stressful because we have to constantly prepare for when this may end."

Proponents of the law are seeking its permanent extension in part because some illnesses may not manifest until years later, after the statute of limitations for worker's compensation or certain state laws may have run out.

The law, which is set to expire in October 2015, established the World Trade Center Health Program to provide medical monitoring and treatment for first responders affected by Sept. 11-related illnesses. It also reactivated the September 11th Victim Compensation Fund, which is set to expire in October 2016.

Rep. Yvette D. Clarke, D-New York, said the law is "more than likely" to be reauthorized. She said the permanence of the law is critical because of the children who may be affected by the delay and persistence of certain illnesses.

"The heavy lifting is done," Clarke said. "We're building a case for why (a permanent law) is a necessity."

The law, called the James Zadroga 9/11 Health and Compensation Reauthorization Act, is named after a New York police officer who participated in rescue and recovery efforts at the World Trade Center after the terrorist attack of Sept. 11, 2001. He died in 2006 from respiratory failure that was said to be related to his Sept. 11 service.

Nearly 15 years later, dozens of firefighters have died and hundreds more are seriously ill with health problems. Howard said there have been rare cancers and chronic health problems found in some victims.

Without the funding provided by the Zadroga Act, research on these illnesses would cease, Howard said.