Chicago - The nation's largest doctors' group urged senators on Friday to stop trying to repeal or replace Barack Obama's Affordable Care Act and instead begin a bipartisan effort to stabilise the insurance marketplace.The American Medical Association (AMA) said proposed Republican bills - one to repeal and replace the 2010 health law, the other to repeal only - would cause too many people to lose coverage."Each bill results in millions more Americans without health insurance coverage, weakened markets, less access to affordable coverage and care, and the undermining of funding for state Medicaid programmes," wrote Dr James L Madara, the group's CEO, in a letter to Majority Leader Mitch McConnell and Minority Leader Chuck Schumer. The doctors' group called for bipartisan co-operation, starting with action to shore up shaky insurance markets."Senators from both sides of the aisle have expressed interest in pursuing remedies to stabilise the individual market and foster greater availability and choice of health plans. We urge Congress to take this initial step," the letter said.The AMA has about 250 000 members.The Congressional Budget Office said on Thursday that McConnell's latest bill would produce 22 million additional uninsured people by 2026 and drive up premiums for many older Americans. Congress' nonpartisan fiscal analyst said on Wednesday the repeal-only bill would mean 32 million additional uninsured people over a decade and average premiums doubling.The AMA letter said the group is willing to work with Congress to address longer terms goals such as unsustainable trends in health care costs.