These and other probable absences from blockbuster shows this year stem from an obscure legal dispute that has turned into a full-scale diplomatic feud between the United States and Russia.
State-run Russian museums, including the Hermitage in St. Petersburg and the Pushkin Museum of Fine Arts in Moscow, are canceling long-scheduled loans to American institutions in response to a decision by an American judge in a case involving Jewish religious documents held by Russia.
The ban is highly unusual. For decades international loans have been the lifeblood of large and lucrative shows, and exchanges between American and Russian institutions have been common. The Met alone has borrowed works from Russian institutions for about 40 shows since 1990. But now, like the National Gallery, it is scrambling to fill holes in heavily promoted exhibitions.
“We are all caught up in a political situation that is not of our making,” said Thomas P. Campbell, director of the Met.
Diplomats in Washington and Moscow have been seeking to negotiate an agreement to pave the way for the loans but have so far been unsuccessful.
The legal dispute centers on the so-called Schneerson Library, a collection of 12,000 books and 50,000 religious documents assembled by the Chabad-Lubavitch Hasidic movement over two centuries prior to World War II, and kept since in Russia.
For decades the Chabad organization, which is based in Crown Heights, Brooklyn, has been trying to regain possession of the library, saying that it was illegally held by the Soviet authorities after the war.