US Democrats furious with Republican secrecy brought Senate business to a standstill, launching an hours-long protest against President Donald Trump's party crafting a back-room Obamacare repeal plan and refusing to hold public hearings about it. Senate Majority Leader Mitch McConnell has said he wants the legislation passed by June 30. Democrats fear he is purposely keeping the bill under wraps until the last minute so he can jam the controversial plan through with just a few hours of floor debate. The strategy is an 180-degree shift from the Republican position during the 2009-2010 debate on Barack Obama's health care reforms when conservatives demanded transparency and dozens of public hearings in a months-long process. In the six weeks since the House of Representatives passed its Obamacare repeal legislation, Senate Republicans have insisted they will craft their own bill, but few details have emerged. With just 10 legislative days before McConnell's deadline, all that most lawmakers and the public have to work on is the House bill, which a non-partisan congressional review predicted would leave 23 million fewer people insured over the next decade. "Republicans are drafting this bill in secret because they're ashamed of it, plain and simple," said Senate Minority Leader Chuck Schumer, shortly before Democrats took to the Senate floor in anger. Republicans argue that Obamacare has failed to prevent premiums and other health costs from skyrocketing. Democrats warn that Trump's delay of government subsidy payments is leading to instability and causing costs to rise. Senator Cory Booker called the Republican strategy "tragic" and broken. "People (are) working in secret on a bill that they're going to try to force through Congress with no public input, no hearings, no meetings, no markups, no debate, no public accountability," he said in the talk-a-thon, which dragged into a fifth hour. Even as McConnell downplays the secrecy, few Republicans appear to know what will be in the legislation. Some have begun speaking out. "If it is an effort to rush it from a small group of people, straight to the floor in an up or down vote, that would be a problem," Senator Marco Rubio told CNN Sunday. Republicans have signaled one of the main internal debates focuses on reforms to Medicaid, the health care program for low-income people. Critics have estimated that the House bill would curtail Medicaid by some USD 800 billion, and some Republican senators from states where Medicaid was expanded under Obama have expressed concern about passing legislation that slashes aid to thousands of constituents. The Senate version is expected to end the Medicaid expansion more slowly than the House bill would, and it could include larger tax credits to help older Americans purchase health insurance. But with no text finalised, it remains a guessing game. "Most Republicans don't have a clue as to what's in this legislation, let alone Democrats, let alone the average American," fumed Senator Bernie Sanders. "So I say to the Republican leadership: what are you afraid of? Bring that bill out." White House spokesman Sean Spicer pointed to "very good" progress on the bill, but he declined to say whether White House aides had even seen a draft. An exchange on the Senate floor late yesterday highlighted the tension. Schumer asked McConnell whether there would be sufficient time to review and debate the legislation. "I think we'll have ample opportunity to read and amend the bill," McConnell said curtly.