Rick Santorum ends his bid for the US presidency

Republican presidential candidate Rick Santorum has dropped out of the presidential race clearing the way for the front runner Mitt Romney.

The former senator from Pennsylvania said he was suspending his campaign, but vowed "we are not done fighting".

The announcement effectively ends Santorum's bid to be the Republican who will face President Barack Obama in the November 6 general election.

Santorum was lagging behind Massachusetts governor Mitt Romney in opinion polls and in the fight for the 1,144 party delegates needed to win the nomination.

A devout Catholic with seven children, Santorum failed to stretch his appeal far enough beyond conservatives and some blue-collar Republicans to be able to overtake Romney.

Santorum did not say if he would endorse Romney or the other two Republican candidates, Ron Paul and Newt Gingrich, both of whom are way behind former Massachusetts governor Romney.