US congressman, Todd Akin

US candidate Todd Akin, who caused uproar by claiming women's bodies could prevent pregnancy in cases of rape, has again refused to stand aside.

Appearing on conservative talk radio, the Republican congressman defied intense pressure from the party to bow out of the Missouri Senate race, reports the BBC.

He has asked to be forgiven for Sunday's remarks on "legitimate rape", which prompted outrage and bafflement.

The gaffe could sink his challenge to Democratic incumbent, Claire McCaskill.

Correspondents say Republicans fear the backlash could endanger their campaign to win control of the US Senate in November's elections.

On conservative radio host Mike Huckabee's show on Tuesday, Akin announced he would not be quitting the race.

He described the response to his comments as a "little bit of an over-reaction", saying he had mistaken "one word in one sentence on one day".

"By taking this stand, this is going to strengthen our country," Akin said. "I hadn't done anything morally or ethically wrong, as sometimes people in politics do."

The sixth-term lawmaker said he was staying in because there were voters who did not feel represented by the major political parties.

Last week Akin had a comfortable lead in opinion polls over Senator McCaskill in the Midwestern state of Missouri, which has leaned increasingly conservative in recent years.

Then on Sunday, he was asked by local news station KTVI-TV about his no-exceptions view on abortion.

The 65-year-old lawmaker replied: "It seems to me, from what I understand from doctors, that is really rare.

"If it's a legitimate rape, the female body has ways to try to shut that whole thing down."

The American Congress of Obstetricians and Gynecologists has said Akin's claim "contradicts basic biological truths".

He also went on Huckabee's radio on Monday to resist calls from prominent Republicans to drop out of the race.

In a face-to-face video message on Tuesday, Akin said: "Rape is an evil act. I used the wrong words in the wrong way, and for that I apologise.

He added: "Fact is, rape can lead to pregnancy. The truth is, rape has many victims. The mistake I made was in the words I said, not in the heart I hold. I ask for your forgiveness."

Republican presidential candidate Mitt Romney and his running mate, Paul Ryan, swiftly distanced themselves from Akin.