Vermont senator Bernie Sanders won the Democratic caucus in Alaska Saturday and held a substantial lead over frontrunner Hillary Clinton in the state of Washington, US broadcasters say.
With 43 per cent of the Alaska vote counted, Sanders had won 79 per cent versus Clinton's 21 percent, MSNBC reports.
In the north-western state of Washington, where 101 delegates are at stake, Sanders was leading Clinton 76.6 per cent to 23.3 per cent with 25 per cent of the ballots counted, according to CNN.
Voters are weighing in at party meetings Washington, Alaska and Hawaii as Clinton hopes to solidify her lead for the centre-left party's nomination ahead of November elections.
Sanders, a longtime member of the US Congress and self-declared democratic socialist, has proven an unexpectedly strong challenger but Clinton continues to be favoured to secure the nomination through the state-by-state nominating process ahead of July party conventions.
Clinton won the Arizona primary on Tuesday, but lost to Sanders in caucuses in Idaho and Utah.
Sanders has done well in states with the party meetings known as caucuses that tend to attract only the most committed party members and where a small number of dedicated supporters can have an outsized impact.
Clinton campaigned in Washington state earlier this week with stops at a union hall and a Native American school, while Sanders held rallies Friday in the liberal bastions of Portland and Seattle.
The candidates have devoted relatively little attention to remote Alaska and Hawaii, states with relatively small populations that are located far from the rest of the United States.
Former president Bill Clinton recorded a telephone call in Alaska urging his wife's supporters to vote, while Sanders' wife made a late appearance in the state, the Alaska Dipatch News reported.
Both Washington and Hawaii are strongly Democratic states in national elections, while Alaska tends to favour Republicans.
Clinton leads the race to secure the most delegates to the party convention that are awarded through the state primary and caucus votes, with some 1,690 to Sanders' 946, according to the New York Times tally.
On the Republican side, Donald Trump leads, but the party establishment has yet to back his candidacy and opponents hope to force an alternate candidate to get the nod in a disputed convention.