President Donald Trump began his four-year term of office with a series of executive orders and actions aimed at dismantling key policies of the Obama administration.

1 WITHDRAW FROM TPP

The new administration said its trade strategy to protect American jobs would start with withdrawal from the 12-nation Trans-Pacific Partnership (TPP) trade pact.

TPP, which the United States signed but has not ratified, had been the main economic pillar of the Obama administration's "pivot" to the Asia-Pacific region in the face of a fast-rising China.

Proponents have expressed concerns that abandoning the pact, which took years to negotiate, could further strengthen China's economic hand in the region.

A White House statement said Mr Trump was also committed to renegotiating another trade deal, the North American Free Trade Agreement, which was signed in 1994 by the US, Canada and Mexico.

2 SCALE BACK OBAMACARE

Mr Trump signed an order giving federal agencies broad powers to unwind regulations created under the Affordable Care Act, including enforcement of the penalty for people who fail to carry the health insurance that the law requires of most Americans.

The order does not describe specific federal rules to be softened or lifted, but it appears to give room for agencies to eliminate an array of taxes and requirements under the healthcare law, also known as Obamacare.

Republicans are pledging a repeal of the law, which has been blamed for sharply rising insurance premiums, and rapid votes on a replacement Bill to prevent coverage gaps.

Obamacare added more than 20 million people on to insurance rolls, lowering the percentage of Americans without coverage from 16 per cent in 2010 to 8.9 per cent last year.

3 NEW WHITE HOUSE WEBSITE

The official White House website has been transformed with a new set of policy pledges.

They include plans to both withdraw from and renegotiate major trade deals, grow the nation's military and increase cyber-security capabilities, build a wall at the southern border and deport undocumented immigrants who have committed violent crimes.

There were also some notable absences, such as Web pages on the issue of climate change and the rights of lesbian, gay, bisexual and transgender individuals.

Also last Friday, Mr Trump signed confirmation papers for his picks for Defence Secretary James Mattis and Homeland Security Secretary John Kelly. The Senate has confirmed their nominations.

He also signed a proclamation for a "national day of patriotism".