The AFL-CIO said it would keep working to obtain "the changes that would allow us to support the bill."

Asbestos, used in building materials, auto parts and other products for decades, has been linked to cancer and other diseases. Injury suits have forced many companies into bankruptcy.

Victims would no longer be able to sue, but would have to go to the fund for payment, under the plan crafted by Senate Judiciary Committee Chairman Sen. Arlen Specter, a Pennsylvania Republican, and Vermont Sen. Patrick Leahy, the ranking Democrat on the committee.

Another potential snag to the fund surfaced Friday. A lawyer representing some existing asbestos trusts warned in a letter the legislation's use of these funds would spark a legal challenge.

Former US Solicitor General Theodore Olson, in an April 18 letter to Republican Sen. John Cornyn, of Texas, said the bill would disrupt those trusts and cause "emotional distress to sick and deserving claimants."

The United Auto Workers, one of largest North American labor unions and an AFL-CIO member, last week endorsed the fund, to be financed by companies facing asbestos lawsuits and their insurers.

Manufacturers and other big companies have thrown their support behind the bill, but insurance firms say it needs substantial changes to attract their support and it is opposed by the Association of Trial Lawyers of America.

Specter is due to hold a hearing Tuesday to try to answer questions about how the fund would work. Five Republicans on the Judiciary committee, including Cornyn, are still pressing for changes before they will back the legislation.

The AFL-CIO said the legislation, as currently written, would eliminate compensation for many lung cancer victims without letting them document asbestos exposure thought CT scans, which are more sensitive than regular X-rays.

The bill would also prevent up to 80,000 individuals with varying degrees of illness from gaining access to any forum for compensation for as long as two years in the event the trust fund is not operational, the AFL-CIO said.