The U.S. Senate on Wednesday confirmed Kelly Craft, a Republican donor who is currently ambassador to Canada, as ambassador to the United Nations, despite opposition from Democrats who criticized President Donald Trump's nominee as too inexperienced for the post.

The Senate backed Craft by a vote of 56 to 34, largely along party lines, moving to end seven months without a permanent U.S. envoy to the world body.

UN ambassador is one of several high-level positions in the Trump administration held for months by temporary appointees as the White House struggles to deal with a chronic, high turnover of top administration officials.

The Senate last week confirmed Army Secretary Mark Esper, a former lobbyist, as secretary of defence, ending a record seven-month period in which the Pentagon lacked a permanent top official.

This week, Director of National Intelligence Dan Coats announced his resignation.

Trump nominated Craft, 57, for the UN post after a recommendation from Republican Senate Majority Leader Mitch McConnell, who represents her home state of Kentucky.

She had faced fierce opposition from some Democrats.

Sen. Bob Menendez, the top Democrat on the foreign relations committee, accused Craft of lacking the "seriousness and professionalism" for the post at the world body.

Craft, the wife of a billionaire coal industry executive, generated controversy shortly after assuming her post in Ottawa by telling CBC News she believed "both sides" of the climate change debate.

However, she acknowledged during her confirmation hearing that climate change is a global threat and pledged to recuse herself from any UN talks on the issue involving coal because of her husband's position.

Menendez on Wednesday released a report that said Craft spent the majority of her time as ambassador to Canada outside of Canada.

Craft's backers called her a tough negotiator on a trade deal with Canada and Mexico who had established decent working relationships with both Republicans and Democrats.

Prime Minister Justin Trudeau congratulated Craft on her new post on Twitter and thanked her for her "work building on the strong Canada-U.S. relationship."

Craft will have the difficult job of defending Trump's "America First" foreign policy and navigating his criticism of the United Nations while getting global diplomats to back U.S. policies.

Trump's first UN ambassador, former South Carolina governor Nikki Haley, announced her resignation in October and left the position at the end of last year.