Republican Rand Paul has become the first presidential hopeful to accept bitcoin donations as part of his campaign.

The libertarian son of former US Congressman Ron Paul is running on the slogan "Defeat the Washington Machine" in his bid to become President in 2016.

Some of his key policies include a flat income tax rate, lessening the authority of the Federal Reserve and cutting government spending to balance the budget.

"Today I announce with God's help, with the help of liberty lovers everywhere, that I'm putting myself forward as a candidate for president of the United States of America," Paul said at a rally in Louisville on Tuesday, 7 April.

"Too often when Republicans have won, we've squandered our victory by becoming part of the Washington Machine. That's not who I am.

"Government should be restrained and freedom should be maximized."

Paul has already raised more than $650,000 through donations made by credit card, PayPal and bitcoin.

"Our campaign will be the most technologically savvy campaign," Sergio Gor, a spokesperson for Paul, told Reuters. "We'll engage across all platforms, from Snapchat to bitcoin."

Last year Paul was one of eight US Congress members to receive bitcoin donations worth $250 as part of an initiative to spread awareness about the cryptocurrency.

The politicians were selected by BitPAC, a political action committee based in Washington, with the expectation that they would be the most open to learning about and utilising decentralised currencies.