"To see Pope Francis visit ancient religious sites, including the biblical birthplace of Abraham, spend time with Grand Ayatollah Ali al-Sistani in Najaf, and offer prayers in Mosul -- a city that only a few years ago endured the depravity and intolerance of a group like ISIS -- is a symbol of hope for the entire world," Biden wrote.

The 84-year-old pontiff's packed three-day visit passed off without a hitch despite concerns about security and the coronavirus pandemic. He covered more than 900 miles (1,400 kilometers) inside the conflict-ravaged country.

Biden, only the second Roman Catholic US president, has dramatically raised the Church's profile in the United States with his regular Sunday attendance at Mass and habit of quoting Biblical and other sacred verses.

Pope Francis' visit to Iraq -- the first ever by a head of the Vatican -- came as Biden is grappling with a complex security challenge in the region where Iranian-backed groups have attacked US bases, triggering air strikes in response.