Iran said Tuesday it will further free itself from the 2015 nuclear deal in defiance of new American sanctions as US President Donald Trump warned the Islamic republic of "overwhelming" retaliation for any attacks.
Tensions between Iran and the US have spiralled since last year when Trump withdrew the United States from the deal under which Tehran was to curb its nuclear programme in exchange for relief from economic sanctions.
The two arch-rivals have been locked in an escalating war of words since Iran shot down a US surveillance drone in what it said was its own airspace, a claim the US vehemently denies.
On Monday, Washington stepped up pressure by blacklisting Iran's supreme leader Ayatollah Ali Khamenei and top military chiefs, saying it would also sanction Foreign Minister Mohammad Javad Zarif later in the week.
Tehran was defiant on Tuesday, saying the new US sanctions against Iran showed Washington was "lying" about an offer of talks.
"At the same time as you call for negotiations you seek to sanction the foreign minister? It's obvious that you're lying," President Hassan Rouhani said.
A top security official said Iran would "resolutely" abandon more commitments under the nuclear deal on July 7.
Iran had announced on May 8 that it was suspending two of its 2015 pledges and gave Europe, China and Russia a two-month ultimatum to help it circumvent US sanctions and sell oil or it would abandon two more commitments.
"As of July 7, Iran will forcefully take the second step of reducing its commitments" to the nuclear deal, Rear Admiral Ali Shamkhani, secretary of Iran's Supreme National Security Council, was quoted as saying by Fars news agency.
This was so "countries who interpreted Iran's 'patience' with weakness and inaction realise that Iran's answer to the American drone's violation of its airspace will be no different than its reaction to devious political efforts to limit Iranian people's absolute rights," he added.
- Trump warns of 'obliteration' -
US national security adviser John Bolton, on a visit to Iran's arch-enemy Israel, said Washington had "held the door open to real negotiations" but that "in response, Iran's silence has been deafening".
Bolton also warned Iran against disrupting a US-led conference in Bahrain on Middle East peace that began Tuesday.
"Iran has engaged over the past couple of months in a long series of unprovoked and unjustifiable attacks," he said.
"In that kind of environment, threatening the conference in Bahrain is always a possibility," said Bolton.
"It would be a big mistake for Iran to continue this kind of behaviour."
Zarif posted a link on Twitter to a 2017 article by Bolton titled "How to Get Out of the Iran Nuclear Deal" as proof he was never interested in talks.
"Iran never left the negotiation table. #B_Team dragged the U.S. out, while plotting for war," the diplomat wrote, referring to Bolton and other hard liners.
Trump earlier warned Iran against any attack on US interests.
"Any attack by Iran on anything American will be met with great and overwhelming force. In some areas, overwhelming will mean obliteration," he tweeted.
Iran and the US broke off diplomatic relations in 1980 over the hostage crisis at the US embassy in Tehran following Iran's Islamic revolution.
Since quitting the nuclear deal and reimposing sanctions on Iran, Trump has moved to choke the country's economy, blacklisted its Revolutionary Guards as a "terrorist organisation" and nearly launched a military strike in retaliation to Iran downing the US spy drone.
Zarif said the drone had violated Iranian airspace, as did Russia -- a key ally of Tehran.
Washington has also blamed Iran for mid-June attacks on two tankers in sensitive Gulf waters, a claim Iran hotly refutes.
Trump has said he is ready to negotiate with Iran "with no preconditions" and that Iran could have a "phenomenal future".
"We do not ask for conflict," he said, adding that depending on Iran's response, sanctions could end tomorrow or "years from now".
But Iran's foreign ministry spokesman Abbas Mousavi said the new sanctions meant "permanent closure of the path to diplomacy with Trump's desperate government".
Rouhani also mocked the logic of blacklisting the supreme leader, who has few assets and no plans to visit the US.
"To sanction (the supreme leader) for what? Not to travel to America? That's cute," he said.
- Diplomacy over? -
Rouhani noted there had been chances for talks between the two sides.
Zarif met former US secretary of state Rex Tillerson several times before Washington unilaterally withdrew from the nuclear deal in May 2018 and reimposed sanctions.
"You do not seek to negotiate. If you did, we could have," Rouhani said.
Zarif, a political moderate, was a key architect of the deal under which Iran agreed to curb its nuclear programme in exchange for sanctions relief.
But both he and Rouhani have accused Washington of waging an "economic war" on Iran since pulling out of the accord.
Amid a flurry of diplomatic activity, the UN Security Council on Monday issued a unanimous call for dialogue to address the standoff between the United States and Iran.
China on Tuesday urged "calm and restraint" as tensions grew.