The carrier group of the USS Carl Vinson has re-entered the Gulf. Another US carrier group, of the USS Abraham Lincoln, continues to patrol the Arabian Sea just south of the Strait of Hormuz.
It is backed by three attack submarines, one of which is carrying 154 Tomahawk missiles.
On Friday, President Obama re-iterated his pledge to do everything in his power to avert the emergence of a nuclear-armed Iran. He said even military action remained an option.