(CBS/AP) The manufacturer of a drug used to inhibit the effects of the bird flu virus will negotiate with generic drug companies to increase production, two senators said Thursday.

Tamiflu is the most effective drug in treating bird flu, a virus that has killed more than 60 people since late 2003, all of them in Asia. Most human cases have been linked to contact with sick birds. But health officials warn the virus could mutate into a form that can be easily passed between humans, possibly triggering a global pandemic which could kill millions.

Swiss-based Roche Holding AG will meet with four companies and maybe more in coming weeks, all in an effort to work out licensing agreements that would allow other companies to produce Tamiflu, which is in great demand throughout the world.

"The bottleneck on Tamiflu has basically been broken," said Sen. Charles Schumer, D-N.Y., who announced the agreement along with Sen. Lindsey Graham, R-S.C.

The two senators met Thursday with George Abercrombie, head of Roche Pharmaceuticals in North America.

Abercrombie did not meet with reporters, but the company issued a statement in which he said the company had already announced that it was willing to meet with companies that may be able to assist in manufacturing additional supplies.

"We continue to take the steps necessary to protect the health of people on a worldwide basis, and to make Tamiflu available wherever it is needed for both seasonal influenza and pandemic stockpiling," he said. "We already have expanded dramatically our own production capability and continue to make significant investments both internally and with partner companies."

He said Roche has a team in place dedicated to assessing the ability of other companies to either produce or provide capabilities in Tamiflu production.

"We want to be sure that they can produce substantial amounts of Tamiflu for pandemic use in a timely manner in accordance with appropriate quality specifications, safety and regulatory guidelines," he said.

Generic manufacturers cannot legally sell the patented drug in the West and parts of Asia. Roche holds the patent. Companies would need a sub-license from Roche to make the drug, Schumer said.

The determination of who gets the sub-license will be made in cooperation with the U.S. government and other governments around the world, the senators said.

Schumer said he contacted Roche two days ago, and he asked company officials to find other drug companies that they would grant a license to. Roche, in return, asked the senator to find some companies that would be willing and able to take on the job.

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