Image copyright Reuters Image caption Critics say Mrs DeVos, who has no experience with public schools, is not qualified to run the Education Department

The US Senate has confirmed President Donald Trump's controversial nominee for education secretary, Betsy DeVos, by the slenderest possible margin.

US Vice-President Mike Pence cast the tie-breaking vote to secure her cabinet role, splitting the chamber 50-50.

It was the first time ever that a vice-president has interceded in such a way for a cabinet secretary.

Mrs DeVos, a billionaire who has no experience with public schools, faced a rocky confirmation hearing last month.

Moments after voting ended, she tweeted: "I appreciate the Senate's diligence & am honored to serve as @usedgov Secretary.

"Let's improve options & outcomes for all US students."

Senate Democrats staged a 24-hour debate into Tuesday to hold up her confirmation.

They hoped their all-night speaking marathon would pressure more Republican senators to oppose the nomination, but their efforts were in vain.

Mr Pence later swore in Mrs DeVos as education secretary.

He was also the first vice-president to cast a deciding vote in the Senate since 2008, when Dick Cheney voted on a tax adjustment plan.

No Democrats voted in favour of Mrs DeVos. Two Republican senators stood by their plan to oppose her confirmation, leaving the Senate in a deadlock.

Image copyright AP Image caption Vice-president Pence (seated left) cast the deciding vote

Analysis - Anthony Zurcher, BBC News North America Reporter

In the end Donald Trump is going to get the team he wants.

Betsy DeVos's education secretary nomination looked a bit shaky for a while, but no Republican senator was willing to be the third "no" vote that would have sunk her.

Secretary of State Rex Tillerson's ties to Russia made some conservatives uneasy, and prompted sharp questioning from Senator Marco Rubio of Florida, but the former oil magnate's party closed ranks behind him.

The only real question mark left is labour secretary nominee Andrew Puzder, whose confirmation hearings have been postponed four times amid reports that he has not fully disentangled himself from his sprawling fast-food business empire.

If he withdraws, however, it will be quietly, before a confrontation with Democrats heats up.

Democrats always faced an uphill battle in bringing down any of Mr Trump's cabinet nominees, given the mathematical reality of being in the Senate minority.

Republicans were loath to deal an early, embarrassing setback to the new president, possibly earning his long-term enmity.

The fight over Mrs DeVos and other nominees has engaged the Democratic base, however.

Now the question is whether they will stay engaged in the months and years ahead - or if this initial surge of activism will recede over time.

Critics say Mrs DeVos is unqualified to run the Department of Education.

She faced intense scrutiny before a Senate committee in January, when she made headlines for noting that a Wyoming school might need a gun to defend against grizzly bears.

Labour unions, rights groups and teaching organisations have also spoken out against her nomination.

Groups including the American Federation of Teachers and the Leadership Conference on Civil and Human Rights held protests against Mrs DeVos outside of Congress on Monday evening.

Image copyright EPA Image caption Mrs DeVos has faced mounting criticism from groups including the American Civil Liberties Union and the American Federation of Teachers

The 59-year-old is a wealthy Republican Party donor and a former Michigan Republican Party chairwoman who has long campaigned for education reform in the state.

She is a champion of charter schools, which are publicly funded but operate outside state school systems.

Her husband Dick DeVos was a chief executive of the beauty and nutrition giant Amway and her brother is Erik Prince, the founder of the controversial private security company Blackwater.

She is among several of Mr Trump's cabinet picks whom Democrats have been trying to block from being approved.

Democrats said in January they would target eight of Mr Trump's nominees based on their lack of qualifications and policy positions.

Before Mrs DeVos' approval, just six of Mr Trump's cabinet picks had been confirmed, compared with former President Barack Obama's 12 cabinet secretaries at this point in 2009 and 16 of George W Bush's in 2001, according to the Washington Post.

The slowed process is also partly due to the fact that some of Mr Trump's picks have not completed a lengthy vetting process typically required of Cabinet candidates, which helps identify potential conflicts of interest.

Hundreds of staff positions also remain vacant as the fate of 15 of Trump administration's nominees hangs in the balance.

Trump's cabinet

Who has been confirmed?

Betsy DeVos - Education Secretary

General James Mattis - Defence Secretary

Mike Pompeo - CIA Director

Rex Tillerson - Secretary of State

Retired General John Kelly - Homeland Security Secretary

Elaine Chao - Transportation Secretary

Nikki Haley - UN Ambassador

Who is still waiting?

Jeff Sessions - Attorney General

Tom Price - Health and Human Services Secretary

Steven Mnuchin, Treasury Secretary

Ben Carson - Department of Housing and Urban Development Secretary

Andrew Puzdner - Labour Secretary

Scott Pruitt, Environmental Protect Agency

Rick Perry - Department of Energy Secretary

Ryan Zinke - Department of the Interior

Wilbur Ross - Department of Commerce Secretary

Sonny Perdue - Department of Agriculture Secretary

Dr David Shulkin - Department of Veterans Affairs

Mick Mulvaney, Office of Management and Budget

Linda McMahon - Small Business Administration

Dan Coats - Director of National Intelligence

Robert Lighthizer - US Trade Representative