Democratic presidential contender Bernie Sanders won nominating contests in Alaska and Washington today, chipping away at front-runner Hillary Clinton's commanding lead in the race to pick the party's candidate for the White House.

Mr Sanders was aiming for a sweep of three Western states - Hawaii was also holding a contest today - that would generate more momentum in his bid to overtake Ms Clinton and help stave off calls from Democratic leaders that he should wrap up his bid in the name of party unity.

"We are making significant in-roads in Secretary Clinton's lead and ... we have a path to victory," Mr Sanders told cheering, chanting supporters in Madison, Wisconsin. "It is hard for anybody to deny that our campaign has the momentum."

Ms Clinton, the former secretary of state, has increasingly turned her attention toward a potential 8 November general election showdown against Republican front-runner Donald Trump, claiming she is on the path to wrapping up the nomination.

Heading into today's voting, she led Mr Sanders by about 300 pledged delegates in the race for the 2,382 delegates needed to be nominated at the July convention.

Adding in the support of super delegates - party leaders who are free to back any candidate - she has 1,690 delegates to 946 for Mr Sanders.

"These wins will help him raise more funds for the next few weeks but I don't think it changes the overall equation," said Democratic strategist Jim Manley, a Clinton supporter. "Hillary Clinton has too big a lead. It's all over but the shouting."

But Mr Sanders has repeatedly said he is staying in the race until the July convention, pointing to big crowds at his rallies and high voter turnout among young and first-time voters as proof of his viability. After raising $140m, he has the money to fight on as long as he wants.

The Democratic race now moves to contests in Wisconsin on 5 April and in New York on 19 April.

There were no contests today in the Republican race featuring Mr Trump and rivals Senator Ted Cruz of Texas and Ohio Governor John Kasich.