US Democratic presidential hopeful Bernie Sanders has won the Wyoming caucuses, extending his winning streak against rival Hillary Clinton.

Sanders clinched victory in the Wyoming Democratic caucuses on Saturday, registering eight wins in the last nine contests, US media reported.

The independent senator from Vermont won 55.7 percent of the Wyoming vote to 44.3 percent for Clinton, with all the ballots counted.

The state awards just 14 delegates on a proportional basis, but the win gives Sanders another morale boost, ahead of the crucial primary in New York state, where voters will cast their ballots on April 19.

Sanders' victory follows rising tensions between the two candidates after he raised the issue this week of Clinton being unqualified to run the country, citing “tens of millions of dollars” she is receiving from special interest groups through her super PAC.

Additionally, Sanders censured Clinton for her support of the invasion of Iraq in 2003, and said that she should apologize to the victims of the Iraq war, which she voted in favor of as a senator.

He softened his tone on Friday, saying his remarks that the Democratic frontrunner is “unqualified” for the job was a response to her recent attacks against him.

Sanders, whose campaign was boosted by landslide victories in Alaska, Washington, Hawaii and Wisconsin, is hoping to cut further into Clinton’s lead in her home state of New York.

Sanders has long been critical of US foreign policy and was an early opponent of the wars in Iraq and Afghanistan. Clinton, in contrast, is almost universally recognized as being far more hawkish and inclined to use military force.

Sanders, 74, is also a leading proponent of issues such as income equality, universal healthcare, parental leave, climate change, and campaign finance reform in the US.

However, the incomes of Bill and Hillary Clinton put them at the upper end of the top 0.1 percent of earners in the US population, according to government data. The exorbitant pay for light work can distance them from the realities most Americans experience at their jobs.