Bernie Sanders is on the way to two big wins as he seeks to make up ground on his Democratic rival Hillary Clinton.
With around 15 per cent of precincts having reported, Mr Sanders was leading on 73 per cent in Washington state while Ms Clinton was on 25 per cent.
In Alaska, the Vermont senator had an even bigger lead. He was on 81 per cent, while the former secretary of state was on 18 points, and CNN projected him as the winner there. The state of Hawaii was holding its caucuses later on Saturday.
Ms Clinton currently has a sizable lead over Mr Sanders in the race for securing the Democratic nomination, with 1223 pledged delegates compared to his 920.
Mr Sanders is trying to build on overwhelming victories earlier this week in caucuses in Idaho and Utah.
However, he also suffered defeat in Arizona, and although his delegate haul from the three states was 20 higher than that of Ms Clinton, he has failed to make major inroads into her lead.
Both candidates have been campaigning in Washington state. Ms Clinton told supporters in Everett: “We are on the path to the nomination, and I want Washington to be part of how we get there.”
Washington is the biggest prize on Saturday, with 101 pledged delegates available. Hawaii has 25 delegates at stake and Alaska 16.
