Newt Gingrich on Tuesday vowed to defend the Defense of Marriage Act (DOMA) and remain faithful to his wife, the San Francisco Chronicle reported.

Gingrich has not signed The Family Leader's controversial 14-point anti-gay marriage pledge, but in a letter to the Christian conservative group he promised to abide by the spirit of the contract.

In a written statement to the Iowa-based group headed by Bob Vander Plaats, Gingrich vowed to “defend and strengthen the family.”

“As President, I will vigorously enforce the Defense of Marriage Act, which was enacted under my leadership as Speaker of the House, and ensure compliance with its provisions, especially in the military. I will also aggressively defend the constitutionality of DOMA in federal and state courts. I will support sending a federal constitutional amendment defining marriage as the union of one man and one woman to the states for ratification. I will also oppose any judicial, bureaucratic or legislative effort to define marriage in any manner other than as between one man and one woman.”

Gingrich, who has acknowledged infidelity in two of his three marriages, also promised to be faithful to his current wife, Callista.

“I also pledge to uphold the institution of marriage through personal fidelity to my spouse and respect for the marital bonds of others,” the 68-year-old Republican wrote.

Gingrich also told the group that he would defend the unborn, religious liberty, the right of the people to rule themselves and against debt.