The US is to send 1,500 troops to the Middle East to counter the "ongoing threat posed by Iranian forces", the acting defence secretary says. Congress has been notified about the plans, Patrick Shanahan said in a statement. Fighter jets, drones and other weaponry will also be deployed. President Donald Trump announced the move earlier on Friday. He said the deployment was "relatively small". A top US official has accused Iran directly of attacking oil tankers. Tensions rose this month after shipping in the Gulf of Oman was damaged by a series of mystery explosions. The US has already deployed an aircraft carrier and bomber planes. But only on Thursday, Mr Trump said that he did not think more troops would be needed. "I don't think we're going to need them," he told reporters. "I really don't. I would certainly send troops if we need them." What is the latest US move?Mr Shanahan said he had "approved a request from the combatant commander for additional resources" in the region. He said the move was intended to "safeguard US forces given the ongoing threat posed by Iranian forces, including the IRGC [Iran's Revolutionary Guard Corps] and its proxies." The IRGC is the most elite military unit in Iran. Last month, the US designated it as a foreign terrorist organisation. Mr Shanahan said that "additional intelligence, surveillance, and reconnaissance aircraft" would be deployed as well as a team of engineers. He said a fighter aircraft squadron and a Patriot missile-defence system would also be sent. It is "a prudent defensive measure... intended to reduce the possibility of future hostilities," Mr Shanahan said. Earlier on Friday, President Trump told reporters outside the White House that a "relatively small" deployment had been approved. "We want to have protection in the Middle East," he said, adding that the extra troops would be "mostly protective." He appeared to downplay the possibility of tensions escalating further. "Right now, I don't think Iran wants to fight and I certainly don't think they want to fight with us," he said.