Iran's army has added 1,000 drones to its combat regiments as its chief vowed a "crushing response" to any attack, state television reported, after the US moved a strike force into regional waters.
"In accordance with the threats we are facing, maintaining and enhancing strategic advantages for rapid combat and a crushing response to any invasion ... is always on the army's agenda," Iran's army commander Amir Hatami said, cited by state television.
Meanwhile, Turkey will offer to mediate between Washington and Tehran during a visit by Iran's foreign minister tomorrow, officials said, as Ankara considers reinforcing security along its border should the dispute escalate.
Tomorrow's visit by Iranian Foreign Minister Abbas Araghchi comes after US President Donald Trump threatened a military strike on Iran over its deadly protest crackdown earlier this month.
Independent groups said Iranian security forces have killed thousands while suppressing mass protests against Tehran's regime.
A US naval strike group arrived in Middle East waters on Monday with Mr Trump warning it was "ready, willing and able" to hit Iran "if necessary".
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Turkish Foreign Minister Hakan Fidan will tell Mr Araghchi tomorrow that his country "is ready to contribute to resolving the current tensions through dialogue", a Turkish diplomatic source said.
Mr Fidan would reiterate Turkey's opposition "to military interventions against Iran ... (over) the regional and global risks such a step would entail", said the source, requesting anonymity because of the sensitivity of the talks.
Yesterday, the minister had stressed the need for Washington and Tehran to resume discussions over the Iranian nuclear programme, suggesting that was the top priority to be resolved.
"It's wrong to attack Iran. It's wrong to start the war again. Iran is ready to negotiate on the nuclear file again," Mr Fidan had told Al-Jazeera television.
"Turkey supports reaching a peaceful solution to Iran's nuclear programme in the near term and is ready to provide assistance if needed in this regard," the foreign ministry source said.
Alongside its diplomatic push, Ankara is assessing additional security precautions along its border with Iran if a US strike destabilises the country, a senior Turkish official said.
"If the United States attacks Iran and the regime falls, Turkey is planning additional measures to reinforce border security," said the official, who also requested anonymity.
Much of the 500km (310-mile) frontier is secured by a wall, but "it has proven insufficient", the official said.
The Turkish authorities have so far avoided the term "buffer zone" but options under review include deploying more troops and expanding technological surveillance systems, the official added.
Turkey began building a concrete wall in 2021 as concerns grew about a potential influx of migrants following the Taliban's takeover of Afghanistan.
So far, officials say there is no sign of mass movement toward Turkey linked to developments in Iran.
Russia joined Turkish calls for diplomacy, saying there was still room for negotiations in the standoff between its ally Tehran and Washington.
"It is clear that the potential for negotiations is not exhausted," spokesman Dmitry Peskov told journalists.
He called for "all sides to show restraint and refrain from methods of force", saying: "Any use of force can only create chaos in the region and lead to very dangerous consequences."
Iran emerged as one of Russia's main allies during the war in Ukraine.
