WASHINGTON (REUTERS) - Tom Price was sworn in as US secretary of health on Friday (Feb 10), putting in place a determined opponent of Obamacare to help President Donald Trump fulfill his pledge to dismantle his predecessor's law and reshape the country's healthcare system.

As head of the Department of Health and Human Services (HHS) Price has the authority to rewrite rules implementing the 2010 Affordable Care Act, also known as Obamacare.

He could move quickly to rework the regulations while waiting for Republicans in Congress to keep their pledge to scrap the law entirely.

The Republican president signed an order on Jan 20, his first day in office, to freeze regulations and take other steps to weaken the law enacted by former Democratic President Barack Obama, a directive that will fall largely on Price. But Trump said in a recent Fox News interview that a replacement for the law may not come until next year.

Trump said on Friday the effort was a "difficult process" but could now get going with Price in place.

"Now we get down to the final strokes," he told reporters at a separate news conference at the White House alongside visiting Japanese Prime Minister Shinzo Abe.

He did not offer more details but said the country would end up with "tremendous healthcare at a lower price."

Republicans, who have long viewed Obamacare as federal overreach and who have the majority in Congress, are trying to craft a replacement but have not agreed on one. Twenty million Americans gained health insurance under the law.

"Having Dr Tom Price at the helm of HHS gives us a committed ally in our work to repeal and replace Obamacare,"said US House of Representatives Speaker Paul Ryan, who has vowed to pass a new plan this year.

Price, a member of the House since 2005 who chaired the budget committee, offered legislation in 2015 to repeal Obamacare and replace it with age-adjusted tax credits for the purchase of health insurance.

While Price's fellow Republicans have controlled the House since 2011, they did not advance his bill and it was not considered by the full chamber.

The Senate voted 52-47 earlier on Friday to approve Price, a former orthopedic surgeon, to oversee the HHS, which has an annual budget of more than $1 trillion.

Price's nomination was dogged by questions about his trading in hundreds of thousands of dollars in health company stocks while working on healthcare legislation. Democrats accused him of making misleading statements. Price defended his actions.

Democrats also criticised Price for his opposition to Obamacare, his ideas about restructuring the Medicare program for the elderly and disabled, and his opposition to Planned Parenthood, an organization that provides abortions and other affordable healthcare and education services.

With Price confirmed, the Senate is expected to vote on Monday (Feb 13) on Trump's US Treasury secretary designate, Steven Mnuchin.