Republican presidential hopeful Marco Rubio made a "pledge to defend the unborn" ahead of the 43rd anniversary of the U.S. Supreme Court's opinion in the case of Roe v. Wade on Friday, Jan. 22.

"Since the Roe v. Wade decision legalised abortion in 1973, tens of millions of children have been denied life, and America has in turn been denied the gifts God gave them," he wrote in an opinion piece for the Quad-City Times.

Rubio then went on to say that life is a definitional issue, and if a society cannot guarantee that the rights of its unborn are upheld, then that "society is not truly equal."

"A nation that cannot guarantee a right to life cannot guarantee liberty. And of course, without life, there is no ability to pursue happiness," he said.

Rubio said the upcoming elections can determine what kind of country and society America will be. The next president of the U.S. can wield great power because he or she can "determine the balance of the Supreme Court for a generation," not to mention enact "pro-life legislation, protect religious liberty, and save millions of lives."

Abortion service provider Planned Parenthood gave Democratic bet Hillary Clinton its seal of approval while giving Rubio a zero percent approval rating. But as a pro-life candidate, Rubio said he is happier with the 100 percent rating he received from the organisation called National Right to Life.

Between the dismal rating given him by Planned Parenthood and the glowing one he received from National Right to Life, Rubio said he does not know "which I'm more proud of."

Should he win the presidency, Rubio vowed to defund Planned Parenthood once and for all with the help of a Republican Congress, reinstate the Mexico City Policy to stop taxpayer funding of abortions overseas, and appoint justices to the Supreme Court who "have a record applying the Constitution as it was written and upholding the God-given rights it protects."

"America is an exceptional nation, one that has been an inspiration to all in search of a better life," he said. "This country tells us we are all equal — that even if we are not born into wealth or power, we can still go as far as our talent and hard work will take us. We know that a culture of life is inseparable from the American Dream. A nation that values life values the dreams we have for ourselves and our children."