The chairman and chief benefactor of the Guggenheim Museum has quit following a row over its future.
The Guggenheim building is due to undergo restoration
Peter B Lewis, who has held the post since 1998, blamed "differences in direction" between himself and museum director Thomas Krens.
The pair were reportedly at odds over plans to turn the New York-based art museum into a global brand.
Mr Lewis, a billionaire, donated about $77m (£41m) to the institution during his time as chairman.
He told the New York Times that he believed the museum "should concentrate more on New York and less on being scattered all over the world".
He had previously expressed his concerns over plans for global expansion, saying Mr Krens had overspent in his quest to build other Guggenheim museums around the world.
The museum has branches in Berlin, Venice, and Bilbao in Spain - but a branch which opened in Las Vegas in 2001 was forced to close after 15 months, while plans for a museum in Lower Manhattan were shelved in 2002.
Mr Krens currently has plans to open a Guggenheim in Rio de Janeiro as well as one in Guadalajara, Mexico. A branch in Taichung, Taiwan, has also been under consideration.
Mr Lewis described Mr Krens as "a man of enormous ability, who will continue to be doing the things he likes to do".
Museum president, William Mack, has been named acting
The Guggenheim Museum, which was designed by architect Frank Lloyd Wright, opened in 1959 on New York's Upper East Side and features around 10,000 works.
In 2004, Mr Lewis contributed $15m (£11.5m) to the planned restoration of the building.