Rand Paul enters Republican race

Conservative US Senator Rand Paul has announced he's running for his party's nomination for the 2016 presidential race, making him the second major Republican to join the contest.

"I am running for president to return our country to the principles of liberty and limited government," Paul said on his campaign website on Tuesday.

Paul, a conservative libertarian who was elected to the Senate in 2010 with strong support from the Tea Party movement, was expected to make a more formal announcement later in the day in Louisville, Kentucky, where he has served as senator since January 2011.

Paul follows Texan Ted Cruz, who launched his candidacy two weeks ago with an appeal to the religious right, among others.

Jeb Bush, brother of former president George W. Bush, leads in opinion polls for the primary elections, although he has yet to officially announce his candidacy.

On the Democratic side, Hillary Clinton has a team and campaign machine in place, suggesting she will announce in the coming weeks.

It was by defying the Republican "establishment" that Paul, now 52, launched his political career in 2009. This was at the start of the anti-tax and small-government movement that would come to exercise a powerful influence within the Republican Party and come to be known as the Tea Party.

Rand Paul prefers the term "libertarian conservative" to describe himself, or a "constitutional conservative," taking care to break with libertarian positions considered too strict or even marginal.

He has pushed against the surveillance programs of the National Security Agency and has promoted criminal justice reform to end mandatory jail term minimums, endearing himself with libertarians.

On foreign policy, he has long been in favour of US disengagement, going as far as proposing an end to all US foreign aid.

He recently proposed a rise in the Pentagon budget. And on gay marriage and abortion, he has moved toward the traditional Republican position against both.

In order to insist to his critics he can break out of the Tea Party mould and rise, Paul has repeatedly cited polls that describe him as the best Republican candidate to take on Clinton.

"Nobody is doing better against Hillary Clinton than myself," he said recently on Fox News.