A moment of silence will be held on Tuesday at a major world summit in memory of the late Polish president Lech Kaczynski and his top officials who died in a plane crash in Russia.
The moment will "mark solidarity between the international community and the people of Poland," said Ben Rhodes, deputy national security advisor for US President Barack Obama.
Leaders and top officials from 47 countries are descending on Washington to discuss the threat of nuclear terrorism Monday and Tuesday. The moment of silence will precede Tuesday's opening plenary session, Rhodes said.
Rhodes said the moment would "underscore that the United States and the world stand with the people of Poland at this time of such great tragedy."
The crash Saturday claimed the lives of 96 people, including Slawomir Skrzypek, head of the central bank; Deputy Foreign Minister Andrzej Kremer; Franciszek Gagor, head of the military chiefs of staff; and Kaczynski's wife, Maria Kaczynska.
The delegation was en route to Katyn, in Russia, to mark the 70th anniversary of the Soviet massacre of 22,000 Polish officers during World War II.