WASHINGTON -- The US military has sunk six Iranian small boats in the Strait of Hormuz, Brad Cooper, chief of US Central Command, said Monday.

The Iranian boats were struck by US Apache and MH-60 Seahawk helicopters, Cooper told a news conference.

US President Donald Trump announced on Sunday that the United States will begin guiding ships out of the Strait of Hormuz on Monday morning, Middle East time.

Cooper dismissed that there are "escorts" of commercial ships by the US Navy in the strait, but said the Pentagon offers "multiple layers" of protection for them.

"If you're escorting a ship, you're playing kind of one-on-one. I think we have a much better defensive arrangement in this process, where we have multiple layers that include ships, helicopters, aircraft, airborne early warning, electronic warfare," he said.

"We have a much broader defensive package than we would have ever if you're just escorting," said Cooper.

Iran later rejected the claim by the United States military that it had sunk several Iranian boats, Iran's semi-official Tasnim news agency reported Monday, citing a senior military official.

Cooper skipped whether the current ceasefire between the United States and Iran will hold, as both sides are reporting new use of munitions.

"I wouldn't go into details of whether the ceasefire is over or not," said Cooper. "I think the key thing is for us is we're merely there as a defensive force and to give a very thick layer of defense to commercial shipping to allow them to proceed out of the (Persian Gulf)."

Earlier on Monday, Iran also dismissed a statement from the US Central Command that two US-flagged commercial vessels successfully passed through the strait.