Iran says a U.S. attack on the Islamic Republic is unlikely because the American military is bogged down in Iraq and Afghanistan.

Iranian Foreign Ministry spokesman Mohammad Ali Hosseini said Sunday that Iran doubts the U.S. would get involved in what he called a "new disaster" which Americans "themselves" have acknowledged would have painful consequences for the region and the world.

Hosseini's comments came two days after the U.S. Navy said a ship under contract to the U.S. military fired warning shots at two approaching boats in the Persian Gulf.

Iran has denied that any of its vessels were involved in an incident with U.S. ships.

The Iranian statements follow comments last week by the Chairman of the Joint Chiefs of Staff, Admiral Mike Mullen, as well as Defense Secretary Robert Gates accusing Iran of stepping up its military support for Iraqi militias.

Mullen said Friday at a Pentagon news conference that U.S. intelligence has seen increased aid to insurgents fighting U.S. and coalition soldiers in Iraq. He also noted similar aid increases flowing to militants and the Taliban in Afghanistan.