The US National Transporation Safety Board said Thursday it will join the probe into the Ukrainian Boeing airliner which went down in Iran.
"The NTSB has designated an accredited representative to the investigation of the crash," said the agency which probes transport accidents.
Countries like UK and Canada have hinted that the crash may have taken place due to Iran's alleged role behind it.
British Prime Minister Boris Johnson said Thursday that there was now "a body of information" that the Ukrainian Boeing 747 that crashed in Iran, was brought down by an Iranian missile.
His comments follow a similar message by Canadian Prime Minister Justin Trudeau.
Canadian Prime Minister Justin Trudeau said "multiple" intelligence sources indicate that Iran shot down the Ukrainian airliner after it took off from Tehran, killing all 176 on board, including 63 Canadians.
US President Donald Trump indicated that Washington officials believed the Kiev-bound Boeing 737 was struck by one or more Iranian missiles before it ditched and exploded outside Tehran.
Iran on Thursday ruled out a missile strike as the cause of a Ukrainian passenger plane crash near Tehran, saying such a scenario made "no sense".
(With AFP inputs)