Santorum unbowed by Romney's widening lead

US: Republican White House hopeful Rick Santorum is unbowed by frontrunner Mitt Romney's widening lead and has vowed to take the fight all the way to the Republican convention in August.

"We're going to pick up a whole boatload of delegates and close this gap and on to victory," Santorum told supporters gathered in Pennsylvania after he lost the Illinois primary by a wide margin on Tuesday.Written off in the early days, Santorum has steadily notched up wins -- 10 out of the past 33 contests -- largely with the help of evangelical Christians and the party's most conservative members.

He aimed to rally those supporters by attacking Romney as an untrustworthy moderate. AFP