Donald Trump has nominated Callista Gingrich, wife of former House Speaker and fervent Trump ally Newt Gingrich, to serve as ambassador to the Vatican.

The White House announced the nomination the same day Mr Trump left for his first trip overseas as president, during which he will stop at the Vatican for an audience with the Pope.

Some in Washington hope Ms Gingrich will be able to patch up relations between the president and the pontiff, who engaged in a war of words over Mr Trump’s proposed US-Mexico border wall during the campaign.

"A person who thinks only about building walls, wherever they may be, and not building bridges, is not Christian,” Pope Francis said at the time.

Ms Gingrich’s nomination may cause controversy among some at the Holy See, however, because of her marriage to Mr Gingrich.

The two became involved while Mr Gingrich was still married to his second wife. He did not divorce her for another six years.

The Vatican, however, has not made a policy of passing judgement on nations’ chosen ambassadors. And Ms Gingrich happens to be a staunch Catholic, who converted her husband to the faith in 2009.

"When Newt became a Catholic, it was one of the happiest moments of my life," Ms Gingrich told The New Yorker in 2012.

Pope Francis gives life advice: in pictures Show all 10 1 /10 Pope Francis gives life advice: in pictures Pope Francis gives life advice: in pictures Pope Francis' guide to happiness Pope Francis: 'Live and let live.' GETTY IMAGES Pope Francis gives life advice: in pictures Pope Francis' guide to happiness Pope Francis: 'Proceed calmly" in life' AFP/Getty Images Pope Francis gives life advice: in pictures Pope Francis' guide to happiness Pope Francis: 'Be giving of yourself to others' AFP/Getty Images Pope Francis gives life advice: in pictures Pope Francis' guide to happiness Pope Francis: 'Even though many parents work long hours, they must set aside time to play with their children' AFP/Getty Images Pope Francis gives life advice: in pictures Pope Francis' guide to happiness Pope Francis: 'Sunday is for family' AFP/Getty Images Pope Francis gives life advice: in pictures Pope Francis' guide to happiness Pope Francis: 'Respect and take care of nature' OSSERVATORE ROMANO/AFP/Getty Images Pope Francis gives life advice: in pictures Pope Francis' guide to happiness Pope Francis: 'Stop being negative' AFP/Getty Images Pope Francis gives life advice: in pictures Pope Francis' guide to happiness Pope Francis: Respect others' beliefs' AFP/Getty Images Pope Francis gives life advice: in pictures Pope Francis' guide to happiness Pope Francis: 'Peace sometimes gives the impression of being quiet, but it is never quiet, peace is always proactive' FP/Getty Images Pope Francis gives life advice: in pictures Pope Francis' guide to happiness AFP/Getty Images

Ms Gingrich was born in Wisconsin, and attended Luther College in Iowa, which is affiliated with the Evangelical Lutheran Church. She studied music while at Luther, and still sings in the the choir of the Basilica of the National Shrine in Washington DC to this day.

Mr Gingrich has said that attending her concerts is what convinced him to convert.

A White House press release on her nomination touted Ms Gingrich’s work as president and chief executive of Gingrich Productions, a multimedia production and consulting company.

She has also written a New York Times best-selling children’s series, and produced public policy documentary films. She is the co-author of the book Rediscovering God in America.