President Obama called a plane crash in eastern Ukraine a "terrible tragedy", at a press conference in Delaware today.
Mr Obama added that the US government were working to "determine" whether there were any Americans on board the downed Malaysia Airlines flight.
He said the US would offer "any assistance" to the operation, adding that his "thoughts and prayers" were with the passengers' families.
Thousands of online users have taken to social media to call for the victims of the Malaysian airliner crash to be returned to loved ones.
United States intelligence officials admitted that they do not know who fired the surface-to-air missile that downed flight MH17.
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