President Donald Trump on Friday signed an executive order aimed at limiting the "burden" of the Obamacare health law that the incoming US leader has vowed to repeal.During the signing in the Oval Office, Trump's chief of staff Reince Priebus described the order as aimed at "minimizing the economic burden" of the 2010 Affordable Care Act, "pending repeal."Doing away with Barack Obama's signature domestic achievement is a top priority for Republicans, who control both chambers of Congress and, since Trump's inauguration Friday, the White House.In their view, Obamacare -- which aimed to ensure healthcare for the millions of Americans who are neither covered by public insurance, nor by their employers -- marked a costly drift toward socialized, European-style medical care.Until lawmakers are able to repeal Obamacare, "it is imperative for the executive branch to... take all actions consistent with law to minimize the unwarranted economic and regulatory burdens of the Act, and prepare to afford the States more flexibility and control to create a more free and open healthcare market," the executive order said.The order instructs the US health secretary and other departments and agencies to "exercise all authority and discretion available to them to waive, defer, grant exemptions from, or delay the implementation of any provision or requirement of the Act" that imposes a fiscal burden or other cost on a state, on consumers, on insurers or on a range of healthcare providers.Trump has pledged to start undoing the divisive health law on his first day in office, while also declaring it inconceivable that poor Americans are locked out of coverage.The president has said the law should be repealed and replaced "simultaneously," a stiff challenge given the complexity of America's vast health care system.Obamacare added more than 20 million people onto insurance rolls, lowering the percentage of Americans without coverage from 16 per cent in 2010 to 8.9 per cent last year.Republicans are pledging a repeal of Obamacare -- which has been blamed for sharply rising insurance premiums -- and rapid votes on a replacement bill in order to prevent gaps in coverage and reassure a restless insurance industry.Only one third of the US population is covered by public insurance -- either Medicare, for those over age 65, or Medicaid for the poorest Americans.Half of all Americans are insured through their employers, according to the Kaiser Family Foundation, while about seven per cent are covered through the so-called individual market, which serves those who are self-employed or are employees without coverage through work.Obama's solution rested largely on requiring that everyone be insured, and providing federal subsidies to those who cannot afford coverage.Republicans deemed the first requirement too coercive, and the latter too costly.