TEHRAN, Jan 9 (Reuters) - Iran's parliament speaker has dismissed U.S. accusations that Iranian boats aggressively approached three U.S. Naval ships in the Gulf this week as part of a "propaganda campaign" against the Islamic state.

U.S. President George W. Bush, speaking ahead of a Middle East trip, on Tuesday said Iran committed "a provocative act" in the Strait of Hormuz when Iranian speedboats approached three U.S. Navy ships and threatened that the ships would explode.

The strait is vital to the world oil trade.

"We have always shown that we believe in peace and avoiding tension," Iranian parliamentary speaker Gholamali Haddadadel was quoted as saying by Iran's English-language Tehran Times daily.

"And we presume that the U.S. media propaganda is part of its psychological and propaganda campaign which it is continuously conducting against Iran," he said in comments apparently made before Bush's statement.

Iran's Foreign Ministry spokesman had on Monday dismissed U.S. concerns about the incident, saying it was a routine contact.

The incident was the latest sign of tension between Washington and Tehran, at odds over Iran's nuclear programme and who is to blame for the violence in Iraq.

The Strait of Hormuz handles 17 million barrels per day of water-borne crude oil, over a third of total global shipments. (Writing by Fredrik Dahl, Editing by Matthew Tostevin)

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