CENTCOM said US forces carried out a new round of defensive strikes in southern Iran, targeting missile launch sites and Iranian boats that were allegedly preparing to lay mines.
It also said strikes were conducted on Qeshm Island near the Strait of Hormuz after attempted Iranian attacks.
The renewed fighting has raised fresh doubts over diplomatic efforts to halt the war.
Iran and the United States had signalled last week that they were making progress towards an initial arrangement to stop the conflict and reopen the strait, but no agreement has been finalised.
Iranian Foreign Minister Abbas Araqchi told Lebanese broadcaster Al Mayadeen that communication with Washington had not been cut off, but that the talks had made no progress.
Tehran has tied any agreement to an end to fighting in Lebanon.
It is also seeking access to billions of dollars in oil revenue, waivers on crude-export sanctions, the lifting of a US blockade on Iranian ports and continued leverage over the Strait of Hormuz.
US President Donald Trump, who is facing pressure to bring down fuel prices, has said preventing Iran from obtaining nuclear weapons remains his top priority. Iran maintains that its nuclear programme is peaceful.
In a podcast interview released on Wednesday, Trump said Iran had agreed not to develop a nuclear weapon and that Iran’s Supreme Leader Mojtaba Khamenei was involved in negotiations.
Later, speaking at the White House, Trump suggested there could be movement in the talks as early as the weekend, without giving further details.
Trump also said the parties were trying to separate the issue of reopening the Strait of Hormuz from the conflict in Lebanon.
The wider war has killed thousands, mainly in Iran and Lebanon, and has caused significant economic disruption by hitting energy flows and commercial shipping.
The conflict has also intensified fighting between Israel and Hezbollah, the Iran-backed Lebanese militant group.
Lebanese security sources said Israeli drone strikes on Wednesday killed at least six people in southern Lebanon and targeted a car south of Beirut.
Israel said it had intercepted a hostile aircraft believed to have been launched by Hezbollah.
Araqchi warned that Iran would respond decisively if Israel attacked Beirut.
Trump also acknowledged in his podcast remarks that he had called Israeli Prime Minister Benjamin Netanyahu “crazy” during a tense phone exchange over the fighting in Lebanon, as Washington pushed for a wider deal.
Netanyahu later told that he and Trump sometimes had tactical differences, but remained aligned on the main issues involving Iran.
