Obama identified the American passenger on Flight MH-17 as Quinn Lucas Schansman. A White House official said Schansman held dual US-Dutch citizen ship. No further information about him was immediately available.
Earlier, US officials said that no passenger had checked in for the flight using a US passport, and that most passengers' nationalities had been confirmed, apart from a small number who might have held multiple passports.
US agencies acquired copies of the passenger list for flight MH-17 on Thursday and checked the names against US government data bases to determine if Americans were on board or if any passengers had connections to militant groups.
No evidence has turned up that any passengers had links with militant groups, one official added.
On Friday, Malaysia Airlines said 154 of the passengers came from the Netherlands, where the flight had departed from on its journey to Kuala Lumpur, the Malaysian capital. The airline said there were 44 Malaysians, 17 Australians, 12 Indonesians and 9 British citizens.
There were four passengers each from Belgium and Germany, three from the Philippines, and one each from Canada and New Zealand. It said four passengers' nationalities were still to be confirmed. The 19-member crew were all Malaysians.
(Reporting by Mark Hosenball; Editing by David Storey, Bill Trott and Bernadette Baum)