The US military will send an additional 1,000 troops to the Middle East as tensions build with Iran.
Acting Defence Secretary Patrick Shanahan said the deployment was in response to “hostile behaviour” by Iranian forces.
The US Navy also shared new images it says link Iran to attacks last week on two oil tankers in the Gulf of Oman.
Washington has accused Iran of blowing holes in the vessels with mines. Iran has denied the allegations.
Tensions were further fuelled on Monday when Iran said its stockpile of low-enriched uranium would next week exceed levels set under the 2015 nuclear agreement.
It recently stepped up production in response to the US tightening sanctions. The 2015 deal, from which the US has withdrawn, curbed Iran’s nuclear programme in exchange for the lifting of sanctions.
Iran’s President Hassan Rouhani said his country did not seek to wage war with any nation and had remained “loyal” to its international obligations.
Overnight, three rockets hit a military base housing US troops north of Baghdad, the Iraqi military said. The US said it was “indirect fire” and did not cause injuries.
No group said it had carried out the attack, though it followed US warnings of an increased threat to US interests in Iraq by Iranian-backed militias.
Announcing the deployment, Mr Shanahan said the US did “not seek conflict with Iran” but the action had been taken to “ensure the safety and welfare of our military personnel working throughout the region to protect our national interests”.
He said the military would continue to monitor the situation and make adjustments to troop levels accordingly.
The 1,000 additional troops being dispatched to the Middle East is presented as a prudent defensive measure by the Pentagon; the recent attacks on the two oil tankers being taken as a clear sign of Iran’s hostile intent.
They join some 1,500 additional troops sent last month. Taken together, these deployments inevitably raise tensions, but they are clearly not in any sense an assault force.
If direct conflict does break out between Washington and Tehran, it will most likely be a sporadic air and maritime battle, not a land campaign.
But what worries Washington is attacks by the Iranian Revolutionary Guard Corps or Iran’s proxies against US troops or facilities in the wider region – hence this latest deployment. –BBC