The US Senate will not vote this week on the latest Republican plan to dismantle Obamacare, lawmakers said Tuesday, after it became clear President Donald Trump's party did not have enough support to pass the measure.

"We've made the decision that since we don't have the votes we will postpone that vote," Senator Bill Cassidy, one of the bill's main authors, told reporters.

Republicans, who had sought to pass health care reform with a simple majority vote before a September 30 deadline, could afford just two defectors in order to pass the bill, but three have declared their opposition.