Former President Barack Obama has spoken out against the latest Republican effort to repeal and replace his signature healthcare law.

Over the past week, a new Republican proposal has breathed life back into the fight to repeal and replace Obamacare – an effort many in Washington thought to be dead when an Obamacare repeal bill failed on the Senate floor in July.

The Graham-Cassidy bill, drafted by senators Lindsey Graham and Bill Cassidy, would give states money in block grants to run their own healthcare programmes.

While many Republicans are speaking positively of the proposal, Mr Obama has said it will increase costs and strip people of their health insurance. He also defended his healthcare law, which has expanded insurance coverage.

“When I see people trying to undo that hard-won progress, for the 50th or 60th time, with bills that will raise costs, reduce coverage and roll back protections for older Americans and people with pre-existing conditions ... it is aggravating,” Mr Obama said during an event sponsored by the Bill and Melinda Gates Foundation.

“It may be frustrating that we have to mobilise every couple months to keep our leaders from inflicting real human suffering on their constituents,” he added. “But typically, that's how progress is won.”

The Graham-Cassidy bill is expected to push millions off of their health insurance and weaken protections for people with pre-existing conditions, according to the progressive Center on Budget and Policy Priorities.

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Meanwhile, Republicans assert that Obamacare has led to increased premiums and destabilised the individual markets for health insurance. They have until the end of the month before procedural rules in the Senate make it more difficult for the party to dismantle the healthcare law.

In a Wednesday morning tweet, President Donald Trump called the Graham-Cassidy bill “GREAT!” and said he hopes Republican senators will vote for it.

“I hope Republican Senators will vote for Graham-Cassidy and fulfill their promise to Repeal & Replace ObamaCare,” Mr Trump tweeted. “Money direct to States!”

In another tweet, Mr Trump slammed Rand Paul, who is so far the only Republican senator to have firmly rejected the bill.

“The Graham-Cassidy bill basically immortalizes Obamacare,” Mr Paul told Fox News, calling the bill “just another big-government boondoggle.”