Senators started to stake out firm positions Friday on a prescription drug benefit (search) for elderly patients, hoping to influence intense negotiations that are expected to start this fall.

Sen. Debbie Stabenow (search), D-Mich., said she was trying to persuade the Senate to move toward the House's position and allow Americans to import cheaper drugs from Canada. Sen. Charles Schumer, D-N.Y., proclaimed he will not let negotiators water down incentives in the Senate bill to drive down prescription costs with competition from generic drugs.

Simultaneously, a group of senators formed a coalition to monitor talks and preserve the core of the Senate's prescription drug bill -- bipartisan agreement to ensure Medicare does not lose out to private plans.

"We are closer than ever to taking this enormous step to help our seniors stay healthy and afford their medicines. This is one thing standing in the way -- partisanship and extreme ideology," said Democrat Edward M. Kennedy of Massachusetts, announcing the formation of the coalition with Republican Olympia Snowe of Maine.

The House and Senate voted in June to expand the 38-year-old Medicare (search) program by giving older Americans help with rising prescription drug costs.

House and Senate negotiators expect a long and arduous debate over the final version of the bill. The two chambers' measures vary widely in their approach to a new prescription drug benefit, as well as steps to give private industry a role and help slow the program's rate of growth.

Stabenow said the final bill should allow Americans to get cheaper medicines from Canada. But reimportation proponents acknowledged they face high hurdles to fight pharmaceutical companies and win Senate passage.

Stabenow wants to adopt House language that incorporates technological safeguards like microchips and color-changing material on drug packaging. She also wants to do away with the Senate's requirement that the Health and Human Services Department (search) certify the drugs. HHS has already shown opposition to the idea on safety grounds.

Fifty-three senators, including 13 Democrats, signed a letter last week in support of HHS certification, saying it is a vital safeguard.

Stabenow said some of the Democratic signatories had indicated they could be persuaded to change their minds. "I think the letter that was signed was very quickly signed just to show support for safety and so on," she told reporters.

Also trying to drive the cost of prescription drugs down, Schumer said he will not give ground on language in the Senate bill promoting quick development and marketing of generic drugs.

Speaking to a panel of Bush administration officials called to a hearing on generic drugs in the Senate Judiciary Committee, Schumer said he will fight for elements that allow companies to go to court to get permission to develop generic drugs without the threat of litigation from the brand-name manufacturer.

"I will not watch and stand by as it is watered down in Congress," Schumer said. "I'm not here for a hollow victory."

Aware of the tug-of-war between the House and Senate bills, a group of senators who described themselves as "spanning the political spectrum" pledged to watch the conference closely and ensure the final bill includes elements that have bipartisan support in the Senate.

They include the following:

--An equal drug benefit for those who use traditional Medicare and those who opt for a private plan.

--Comprehensive coverage for low-income seniors with incomes below 160 percent of the poverty line.

--A government fallback for people who live in rural areas without private drug benefit options.