Expressing his desire to bear witness to "the truth," Pope Francis is returning three marble fragments that were originally from the Parthenon in Athens, Greece, according to the Vatican.

The pope will donate the pieces to Orthodox Archbishop Ieronymos II of Athens and All Greece. The archbishop has a degree in archaeology and served as academic assistant at the Athens Archaeological Society, according to the Church of Greece website.

"As a concrete sign of the sincere desire to continue on the ecumenical journey of bearing witness to the truth," Pope Francis has decided to donate the pieces to the Greek Orthodox primate, the Vatican said in a communique Dec. 16.

"The three fragments from the Parthenon have, for centuries, been carefully kept in the pontifical collections and in the Vatican Museums and exhibited to millions of visitors from all over the world," the statement said.

The fragments -- depicting the head of a horse, the head of a bearded man and the head of a boy -- all "came into the Vatican in the 19th century," according to the Vatican Museums' website. The museums' catalogue card for the horse head said it has been in the Vatican collections since 1823; the cards for the other two pieces did not have an acquisition date.

They had been part of the decorative sculptures of the famous Greek temple built on the Acropolis by Pericles in the 5th century B.C., it said.

The announcement of the donation comes the same month in which news outlets reported that senior officials from Greece, including its prime minister, Kyriakos Mitsotakis, have been in secret "preliminary" talks with the British Museum about its huge collection of marble sculptures from the Parthenon.

Mitsotakis has made the repatriation of the collection a priority, The Guardian newspaper reported Dec. 3. "We have seen progress," he said, and a "win-win solution" was possible.

The British Museum maintains it is the rightful and legal owner of the marbles, which it acquired from Thomas Bruce, the Earl of Elgin, who claimed he had permission to remove the sculptures in the early 1800s after approval from the government of the Ottoman Empire, which was ruling Greece at the time.

The British Museum website said that "all surviving examples of decoration from the Parthenon are found in museums; there are fragments in Paris, the Vatican, Copenhagen, Munich, Vienna, Palermo and Würzburg. Of the 50% of the original sculptures that survive, about half are in the British Museum and half in Athens."

The Acropolis Museum in Athens has sought to re-create the complete 525-foot frieze with plaster casts of all the sculptures in foreign collections together with original pieces that were left behind or returned.

The Vatican had loaned the fragment of the boy's head in late 2008 for one year and it was displayed in the Acropolis Museum following a request for its return by the late Greek Orthodox Archbishop Christodoulos at a meeting with Pope Benedict XVI in 2006.

"All the artifacts in the museum belong to the pope, only he can make a decision" about them, Giandomenico Spinola, head of the Vatican Museums' archaeological collections, told Reuters at the time of the loan.