Trump chalks up Washington primary win

AAP

Republican frontrunner Donald Trump has chalked up victory in a presidential primary in the western US state of Washington.

Among Democrats, Hillary Clinton came out on top in a contest that had mostly symbolic meaning because both the Democratic and Republican races for the presidential nomination are all but settled.

Trump won 76 per cent of the vote, according to the official tally.

Even though Senator Ted Cruz of Texas and Ohio Governor John Kasich have dropped out of the race, they picked up about 10 per cent each.

The state's primary is held by mail, and their names were already printed on the ballots when they were posted early this month.

The victory means Trump will claim part of Washington's 44 Republican delegates proportional to his winning percentage. They will be added to the 1,104 delegates he already has, according to the New York Times.

Trump became the presumptive nominee on May 3 after winning the Indiana primary, prompting Cruz and Kasich to abruptly exit the race.

Since he has not yet clinched the nomination, the Washington state primary was important to the celebrity business mogul, who campaigned there earlier this month.

He will remain in the hunt for the 1,237 needed to clinch the nomination through June 7, when California, New Jersey, New Mexico, Montana, North Dakota and South Dakota hold primaries.

Candidate for the Democratic Party's nomination Bernie Sanders had already won his party's caucuses held in Washington state in March, and gained the lion's share of the delegates.

But the state voted again in a primary on Tuesday, revealing a win for front-runner Clinton with 54 per cent of the vote to Sanders' 46 per cent.

Voters were told they could choose either candidate even if they had already participated in the caucuses.

But with delegates already selected in the March 26 vote, the result will be disregarded by the state Democratic Party.