Jolie, Pitt and their son Pax attended a private viewing at the Los Angeles County Museum of Art on Wednesday, and the Oscar-winning actress was wearing the large, rectangular diamond ring on her left hand, a museum spokeswoman told Reuters.

Photos of the three, with Jolie wearing the ring, were released to the media, and jewelry designer Robert Procop said he had designed the ring in collaboration with Pitt, specifically for the actress.

"The full creative journey - from conception to completion - took a year, with Brad Pitt waiting until the perfect moment to unveil this special jewel to Angelina Jolie," Procop's spokeswoman said in a statement on Friday.

Pitt and Jolie have been a couple since 2005, and are raising six children together, but they have never married.

Representatives for the couple, dubbed Brangelina by celebrity media, were not immediately available for comment on Friday about the possibility of an official engagement to marry.

(Reporting By Jill Serjeant; Editing by Bob Tourtellotte)

• A Permanent Economic Emergency