Iran's foreign minister has dismissed US President Donald Trump's claim that a war between their countries would be short-lived, as Washington sought NATO's help to build an anti-Tehran coalition.
"'Short war' with Iran is an illusion," Mohammad Javad Zarif wrote on Twitter on Thursday, a day after Trump said he did not want a war with Iranbut warned that if fighting did break out, it "wouldn't last very long".
Tehran has accused the United States of "economic terrorism" and "psychological warfare" over the Trump administration's application of punishing sanctions after the US president last year unilaterally withdrew Washington from an historic nuclear deal with world powers. Under the 2015 agreement, Iran agreed to scale back its nuclear programme in exchange for the lifting of economic sanctions.
In his Twitter post, Zarif said the reimposed and tightened US sanctions "aren't an alternative to war - they are war".
Also on Thursday, Iran's parliamentary speaker warned the US against violating the country's borders, cautioning such a move would draw a "stronger" reaction than the downing of a US drone a week ago.
In comments carried by Iran's semiofficial Tasnim news agency on Thursday, Speaker Ali Larijani said the shootdown of the unmanned aerial vehicle was "a good experience for them to avoid any aggression".
"Iran's reaction will be stronger if they repeat their mistake of violating our borders," Larijani said.
Tehran said the Global Hawk surveillance drone was in its territory when it was shot down by a surface-to-air missile on June 20. Washington rebuffed that claim, saying the aircraft was in international airspace over the Strait of Hormuz when it was hit.
Trump ordered retaliatory attacks on Iranian installations over the incident - which marked the first direct Iranian-claimed attack on US assets amid an escalating crisis between the two powers - before calling them off at the last minute. The US president later said too many people would have died had the attacks gone ahead.
The war of words between Washington and Tehran has since escalated, with Trump this week threatening Iran's "obliteration" after President Hassan Rouhani called the White House's actions "mentally retarded".
On Wednesday, Trump said any war between Iran and the US would be swift, but reiterated his desire to avoid a military confrontation.
The US leader has been a frequent critic of Iran's leaders, accusing them of sowing disorder and unrest in the Middle East.
Amid rising tension, the acting US defence chief on Thursday pressed NATO allies to join Washington's efforts to squeeze Iran and ensure the safety of ships in the Gulf after a series of mysterious incidents that caused damage to commercial ships near the shipping lane of Strait of Hormuz, which the US has blamed on Iran over Iranian denials.
Mark Esper urged allies to "consider public statements condemning Iran's bad behaviour and making the point that we need to have freedom of navigation in the Strait of Hormuz".
He also sought to "internationalise" the Iran issue, at a meeting of NATO defence ministers in Brussels devoted to discussing the Iran-US crisis.
Tehran said earlier this month it would breach the limit of its stockpile of low-enriched uranium mandated under the deal by Thursday, and threatened to take further steps on July 7 to increase uranium enrichment purity levels over the 3.67 percent limit set in the agreement.
Citing unnamed diplomats, the Reuters agency reported Iran was still short of the cap on enriched uranium, however, but was on course to reach that limit at the weekend.
Tehran's announced plan to breach the deal was widely interpreted as a bid to ramp up pressure on the agreement's remaining signatories - the United Kingdom, France, Germany, China and Russia - to deliver protection from the US sanctions for Iran's faltering economy.
Iran's European partners are expected to announce a multimillion-dollar credit line at a summit in the Austria's capital, Vienna, on Friday.
The credit line is aimed at keeping alive economic ties between European governments and Tehran by helping a special mechanism establish a route for trade between Iran and the West, unnamed officials told the Wall Street Journal on Thursday.
Amid European efforts to salvage the deal, US officials also launched a diplomatic campaign to rally their allies in the face of the escalating crisis.
US Secretary of State Mike Pompeo jetted to the Middle East on Monday to meet leaders of Saudi Arabia and the United Arab Emirates, Gulf Arab states that favour the toughest possible line against Iran.
On Thursday, the US special representative for Iran, Brian Hook, will meet British, German and French officials in Paris for talks.
Hook is expected to receive a frosty reception from Washington's European allies, who support the nuclear deal and believe Trump's decision to quit the accord was a mistake that has strengthened Iran's hardline faction, weakened its pragmatists, and raised the prospect of open conflict in the Middle East.
Since quitting the deal, Trump has deployed more military assets to the region along with thousands of additional troops.
The moves coincided with a series of mysterious attacks on oil assets in the Gulf that Washington has blamed on Tehran, which has in turn repeatedly denied responsibility for the explosions.