The biggest prize was Washington state, but Mr Sanders also won in Alaska and Hawaii, boosting his campaign.

He took at least 70% of the vote in all three states.

Mr Sanders thanked his supporters and said his “campaign has the momentum”, but he still faces a tough task to overhaul Mrs Clinton.

After Saturday’s caucuses, she leads Mr Sanders by 1,243 delegates to 975, the Associated Press count shows.

When superdelegates – party officials who can support either candidate – who have so far declared their allegiance are included, Mrs Clinton is ahead by 1,712 to 1,004 in the race to reach 2,383 delegates.

Bigger battles ahead

Washington was the most significant of the three states voting on Saturday, with 101 delegates up for grabs. There were 16 delegates on offer in Alaska and 25 in Hawaii.

Mr Sanders won 73% of the vote in Washington against 27% for Mrs Clinton, AP reports.

He won a massive 82% of the vote in Alaska, against 18% for Mrs Clinton. In the Hawaii caucus, Mr Sanders won by 70% to 30%.

In total, Mr Sanders won 55 delegates and Mrs Clinton secured 20. More delegates from Washington will be allocated in coming weeks.

Celebrating via Twitter, Mr Sanders said: “Thank you, Alaska! Together we are sending a message that this government belongs to all of us… Washington, thank you for your huge support! It is hard for anybody to deny that our campaign has the momentum.”

Mr Sanders earlier told supporters in Wisconsin: “This is what momentum is about. Don’t let anybody tell you we can’t win the nomination or win the general election. We’re going to do both of those things.”

Mr Sanders had spent the week on the west coast, rallying support among liberals and the left-wing.

Mr Sanders was trying to build on overwhelming victories in last Tuesday’s caucuses in Idaho and Utah.

However, he suffered defeat in Arizona, and although his delegate haul from the three states was 20 higher than Mrs Clinton, he failed to make major inroads into her lead.

Mrs Clinton pointed out last week that she had “2.6 million more votes” than Mr Sanders.

She campaigned less in the three states that voted on Saturday, perhaps expecting the defeats, and spent Easter with her family.

Despite Saturday’s results, the battle will be won and lost in far bigger states still to come. In RealClearPolitics poll averages, Mrs Clinton has the lead over Mr Sanders by nine percentage points in California, 34 points in New York and 28 in Pennsylvania.

Calculations suggest Mr Sanders may need to win two-thirds of the remaining delegates – in primaries, caucuses and among so-far uncommitted super-delegates – the unelected officials who can vote for their candidate of choice at the party’s election convention.

‘Ripped off’

There was no voting in the Republican race on Saturday.

Donald Trump leads Ted Cruz by 739 delegates to 465, with a total of 1,237 needed to win the Republican nomination, according to AP.

Mr Trump has meanwhile given more details about his planned foreign policy.

He told the New York Times he was not an isolationist, but was concerned that America had been let down by its partners and allies.

He said: “We have been disrespected, mocked and ripped off for many, many years by people that were smarter, shrewder, tougher.

“So America first, yes, we will not be ripped off anymore. We’re going to be friendly with everybody, but we’re not going to be taken advantage of by anybody,” he said.

The delegate tracker

Winning delegates, the people who endorse a candidate at the party conventions in July, is key to securing the nomination.

The Democratic totals include the delegates won per state, as well as so-called “unpledged” or “super delegates”. Hillary Clinton has a huge lead among the party leaders and elected officials who each get a vote at the convention.

AP conducts surveys of these super delegates, and adds them to a candidate’s totals if they indicate their support. But super delegates can – and do – change their minds during the course of the campaign, so the figures may shift as the race unfolds.

Source: BBC