The U.S. State department is planning to close its embassy to the Holy See, citing security concerns without naming a specific threat. Ireland announced its decision to shut its embassy to the Vatican in 2011.

The U.S. embassy, which has been in operation since 1984, will be swallowed up by the larger U.S. embassy to Italy, The Daily Beast reports.

Most countries have two embassies in Italy – one to the country of Italy and another to the Holy See, a sovereign nation within Rome. Some, including the U.S., have a third embassy to the United Nations Organization headquartered in the city.

The U.S. embassy to the Holy See is scheduled to move to the American embassy to Italy in January 2015 and will inhabit a small annex with a separate entrance.

Conservative Catholics in the U.S. oppose the move. James Nicholson, a former American ambassador to the Holy See from 2001 to 2005, told Vatican expert John Allen that the move was "a massive downgrade."

Speaking to Allen for the National Catholic Reporter, Nicholson said: "It's turning this embassy into a stepchild of the embassy to Italy."

"The Holy See is a pivot point for international affairs and a major listening post for the United States," he said, "and to shoehorn [the U.S. delegation] into an office annex inside another embassy is an insult to American Catholics and to the Vatican."

Former Bush envoys Francis Rooney and Mary Ann Glendon as well as Raymond Flynn, the first Clinton ambassador, and Thomas Melady, who served the first President Bush, also object to the move.

The Vatican has long insisted that countries with diplomatic missions to both Italy and the Holy See maintain autonomous embassies.

Sources inside the American embassy in Rome have said the embassies will maintain separate functions, reports The Daily Beast. While the U.S. embassy to Italy has a strategic role in American activities in Europe, Africa and the Middle East, its embassy to the Holy See has a distinct role in church affairs.

The action of the embassy to the Holy See follows a similar move by the U.S. embassy to the United Nations Organization, which was moved to the embassy grounds in 2012. Other major countries have also consolidated their embassies, including Israel, the United Kingdom and the Netherlands. Ireland, which closed its embassy to the Holy See entirely, relies on visiting envoys to maintain diplomatic relations.

The Vatican has not commented on the reports of the American embassy closure, but reports say it is unlikely to protest the relocation.