VATICAN CITY — Pope Benedict XVI on Wednesday named an Italian prelate who has served in Vatican diplomatic missions in Iraq, Britain and Nigeria as the new papal ambassador to the United States.

Archbishop Carlo Maria Vigano, 70, who has been serving as secretary-general of the Vatican city-state, takes the place of Archbishop Pietro Sambi who died in July of complications from surgery.

The Washington post is a key one in the Vatican diplomatic corps both for the importance of the U.S. in world affairs and for its large Catholic population, which is counted on for its financial help to the Holy See and its contributions to papal charities.

The appointment comes during the sensitive time of an election year. Catholics make up about a quarter of the American electorate, but they don’t vote as a bloc.

Under Benedict the Vatican has maintained cordial relations with the Obama administration despite deep differences over its support for abortion rights. Some American bishops have taken a harder public stand toward Obama than the Vatican.

Sambi, the late envoy, helped arrange a meeting between clerical sex abuse victims and Benedict that was one of the focuses of the pope’s 2008 visit to the United States.

The Vatican maintains diplomatic relations with 178 countries, most of which maintain two embassies in Rome: one for Italy and one for the Vatican.