Republican US presidential candidate Donald Trump gestures to supporters while speaking in Bismarck, North Dakota, US, May 26, 2016. [Photo/Agencies]

WASHINGTON -- Donald Trump, the presumptive Republican presidential nominee with no remaining rivals, on Thursday garnered the 1,237 delegates needed to secure the nomination, according to the latest Associated Press delegate count.

Trump now has 1,238 delegates after a number of the party's unbound delegates said they would support the New York billionaire at the Republican national convention in July.

"I think he has touched a part of our electorate that doesn't like where our country is," said Pam Pollard, the Republic chairwoman in the state of Oklahoma who is among these unbound delegates.

The Republican primary effectively ended when the New York billionaire won the crucial victory in the Indiana primary earlier this month. His last two remaining competitors at the time, Texas senator Ted Cruz and Ohio governor John Kasich, quitted within 24 hours afterwards.

Since then, Republicans have gradually, though many of them reluctantly, rallied behind Trump, helping him narrow the gap with Democratic frontrunner Hillary Clinton among voters nationwide while heading toward the general election in November.

The real estate mogul's unexpected victory in the primary has also caused a wave of worldwide surprise and bewilderment.

Earlier on Thursday, US President Barack Obama said during his trip to Japan that world leaders are "rattled" by Trump "for good reason."

The world leaders "are not sure how seriously to take some of his pronouncements but they're rattled by him -- and for good reason, because a lot of the proposals that he's made display either ignorance of world affairs or a cavalier attitude," Obama said.