U.S. House Speaker Paul Ryan holds a news conference following a private meeting with Republican U.S. presidential candidate Donald Trump on Capitol Hill in Washington D.C., the United States, May 12, 2016. [Photo: Xinhua]

Paul Ryan, the GOP House Speaker, has finally endorsed the party's presumptive nominee Donald Trump, after weeks of saying he was not ready to do so.

The GOP House Speaker tweeted Thursday afternoon, saying he will vote for Donald Trump.

Ryan also said in this tweet that he is confident Trump will help turn the House GOP's agenda into laws. He then attached a link of his column in his hometown newspaper, the Janesville Gazette, explaining his decision.

In the column, he said the House Republicans would start introducing a series of policy proposals to help improve the American people's lives. And to enact these ideas, he said, America "needs a Republican president willing to sign them into law".

Ryan shocked the world last month by saying he was not ready to support Trump. And Thursday's endorsement is a big boost for Trump, ending an extraordinary public split between the party's presumptive presidential nominee and its highest-ranking public official.

Newt Gingrich, a former House speaker who is tipped as a possible Trump running mate, praised Ryan immediately after the announcement.

Ryan made it clear that the goal of his endorsement is to unite the party to win the general election in fall.