U.S. Senate Majority Leader Bill Frist has raised doubts about a Democratic proposal that would leave some asbestos claims in court while setting up a victims’ compensation fund, a letter circulated on Tuesday said.

Industry would not pay for a large asbestos compensation fund if some victims of the mineral were allowed to pursue their cases in court at the same time, Frist, a Tennessee Republican, told Senate Democratic Leader Tom Daschle in the letter.

“The business and insurance communities simply are not willing to fund a $140 billion trust and, simultaneously, leave open the tort system as your proposal envisions,” Frist told Daschle in the letter dated July 30.

Frist asked Daschle, a South Dakota Democrat, to let him know as soon as possible “whether you thought you could move in our direction” on the matter. “If the answer is in the affirmative, we stand ready and willing to try to work out those critical issues, as well as the remaining provisions of the bill,” he said.

A spokesman said Daschle still hoped for an agreement with Frist on an asbestos victims’ compensation fund, but wanted to address the subject comprehensively.

“Senator Daschle believes that we should continue making progress in these negotiations, by dealing with the issue comprehensively,” the spokesman said.

Asbestos was widely used for fireproofing and insulation until the 1970s. Scientists say inhaled fibers are linked to cancer and other diseases. In recent years hundreds of thousands of injury claims have been filed, forcing companies to pay out $70 billion in compensation to date.

With many more claims expected in the future, Frist and Daschle have been trying to agree on the outlines of a fund that would pay victims, while ending their right to sue. The fund would be financed by asbestos litigation defendants and insurers.

After months of talks, both men are now discussing a fund in the neighborhood of $140 billion to $145 billion. But the question arises what to do with existing asbestos claims that have not worked their way through court.

According to sources close to the talks, Daschle has proposed allowing asbestos cases for which a trial date has been set to proceed in court. Frist however wants existing claims to revert to the new fund, except in cases where there is a final court judgment.