Congress has a few days left to decide the future of one of the legacies of the Sept. 11 attacks, federal backup for terrorism insurance sought by the nation's builders and investors.

The 2002 Terrorism Risk Insurance Act is not as well known as the Patriot Act, another post-9/11 measure Congress is now struggling to renew, but the insurance industry warns that the entire economy could suffer if it loses this cushion needed to offer coverage for catastrophic losses from acts of terrorism.

TRIA, as it is called, expires on Dec. 31, and the House and Senate are still trying to iron out differences between two bills they previously passed.

"Given the overwhelming support both in the House and Senate, we remain optimistic," said Martin DePoy, spokesman for the Coalition to Insure Against Terrorism, the industry group promoting the legislation. He said the coalition doesn't have a preference as long as Congress does something. "Time is running out," he said.

The White House, however, has made clear it does have a preference — the Senate bill.

The administration supports renewing TRIA, but only if it is clear that the program is temporary and that terrorism insurance must ultimately be handled by the private market.

Both the Senate bill, passed by a voice vote last month, and the House bill, approved Dec. 7 on a 371-49 vote, attempt to do that. They raise industry deductibles and co-payments and increase the financial stake of insurers.

Both bills, two-year extensions, would increase the amount of property and casualty losses that would trigger federal payments from the current $5 million to $50 million in 2006 and $100 million in 2007.

But the White House objected to several provisions in the House bill it said would expand the program: The House goes beyond property and casualty insurers to include group life insurance and it provides government backing for domestic terrorist events such as the 1995 Oklahoma City bombing.

"The private market for these lines of coverage has remained robust and competitive, absent a federal backstop," the White House said in a statement to lawmakers. "Adding new lines to the federal reinsurance backstop sends the wrong signal to the marketplace, which should be encouraged to find new ways to diversify the risks of doing business."

The House also specifies that nuclear, biological, chemical and radiological attacks qualify for federal risk insurance backup. In addition, the House bill includes a provision by Rep. Debbie Wasserman Schultz, D-Fla., saying companies can't deny life insurance coverage on the basis of legal travel to countries that the companies deem dangerous.

Peggy Peterson, spokeswoman for House Financial Services Committee Chairman Michael Oxley, R-Ohio, said the House bill "has a great deal to recommend it to taxpayers," mainly a provision that would require insurers to eventually pay back all assistance they get from Washington. She said it contained market reforms, including a public-private commission to come up with ideas for a long-term pooling program.

Julie Rochman, senior vice president for public affairs for the American Insurance Association, said her group doesn't believe catastrophic terrorism is wholly insurable without government help. "We can't simply walk away from the risk," she said, but "essentially we are forced to be in this market."

"We're just trying to get through the next few years," she said. "If they choose to let it expire, we think it would be a huge mistake."

Andrew Gray, spokesman for Senate Banking Committee chairman Richard Shelby, R-Ala., said talks on a compromise are taking place but added that the Senate version had a better chance of becoming law.

"Sen. Shelby views our bill as the appropriate bill for an extension in terms of giving the private sector greater incentive to develop and eventually take on the risk associated with providing insurance for terrorism," he said.