A Sudanese woman who was sentenced to death for refusing to recant her Christian faith has arrived in Italy en route to the United States along with her family, including an infant born in prison.

Italian Premier Matteo Renzi welcomed Meriam Ibrahim at Rome's Ciampino airport, calling it "a day of celebration".

Ms Ibrahim and her family are expected to spend a few days in Rome before heading to the US, where her Sudan-born husband has citizenship.

The Vatican confirmed that Ms Ibrahim will meet with the Pope, but declined to offer further details.

Ms Ibrahim, whose father was Muslim but whose mother was an Orthodox Christian from Ethiopia, was sentenced to death over charges of apostasy.

She married her husband, a Christian, in a church ceremony in 2011.

As in many Muslim nations, Muslim women in Sudan are prohibited from marrying non-Muslims, though Muslim men can marry outside their faith.

The sentence was condemned by the US, the United Nations and Amnesty International, among others, and both the US and Italy - a strong death penalty opponent with long ties to the Horn of Africa region - worked to win her release.

Sudan's high court threw out her death sentence in June, but she was then blocked from leaving the country by authorities who questioned the validity of her travel documents.

Ms Ibrahim arrived in Italy with her husband Daniel Wani, her 18-month-old son and an infant born on May 27.

Lapo Pistelli, an Italian diplomat who accompanied the family from Sudan, said Italy was able to leverage its ties within the region, and "we had the patience to speak to everyone in a friendly way. This paid off in the end".