New Jersey governor and former Republican candidate Chris Christie is endorsing frontrunner Donald Trump for president, he has announced.

Christie dropped out of the 2016 presidential race after a lacklustre showing in polls and state races.

"I'm happy to be on the Trump team and I look forward to working with him," said Christie during a press conference.

Trump gives Republicans the best chance to win the White House, he adds.

He said junior senators Ted Cruz and Marco Rubio, both running for president, were "unprepared" for the job.

There is "no question" that Trump will turn around Washington, Christie continued, and keep Democratic candidate and former Secretary of State Hillary Clinton from winning the White House.

Frontrunner Donald Trump, a businessman from New York, is leading in many state polls and has already won three consecutive state contests in New Hampshire, Nevada and South Carolina, despite never having worked in politics.

He shouldered some criticism from Rubio and Cruz at a Republican debate on Thursday but it is not yet clear whether this has hurt his popularity.

(BBC)