US Senate candidate Todd Akin said on Wednesday that vice presidential hopeful Paul Ryan had asked him to step down over his remarks on rape and that he was "looking at this very seriously."

Akin sparked controversy earlier this week by falsely declaring that in cases of "legitimate rape" a woman's body will often prevent conception, sparking outrage and leading top Republicans to call on him to step down.

In an interview with NBC's "Today" show Wednesday, Akin confirmed that Paul Ryan, a fellow Republican congressman, had asked him to step aside.

"He advised me that it would be good for me to step down," Akin said. "I told him that I was going to be looking at this very seriously, trying to weigh all the different points on this."

He went on to say, however, that his victory in Missouri's Republican primary was "a decision made by the citizens of our state and not the party bosses," indicating that he was still leaning towards staying in the race.

The firestorm unleashed by Akin's initial remarks brought the sensitive issue of abortion front and center on the eve of next week's Republican National Convention, where White House hopeful Mitt Romney had hoped to keep the focus on President Barack Obama's stewardship of the struggling economy.

Romney has led a chorus of calls for Akin to step aside, saying his comments were "offensive and wrong" and that "he should very seriously consider what course would be in the best interest of our country."

Akin apologized again on Wednesday for having "misspoken."

"There is no rape that is legitimate. It's a heinous crime, one of the most serious. I understand that the victims are harmed for a long time and I take that very seriously," he said.

But a Missouri deadline for him to quit the race passed late Tuesday without him dropping out, and in an interview earlier in the day the staunchly pro-life conservative had insisted he would remain in the race.

"I believe there is a cause here," Akin said on former Arkansas governor Mike Huckabee's radio show, insisting that he was getting "a great deal of grass roots support."

"The defense of the unborn and a deep respect for life (are) important parts of who we are, and they're not things to run away from."