Iran is to host a high-level team from the UN nuclear watchdog as part of efforts to defuse dire international tensions over its atomic activities through dialogue.
But other words being spoken in Israel, the United States and Britain -- and Iran's defiant moves to boost its nuclear activities -- underlined the prospect of possible Israeli military action against the Islamic republic.
Iran also signalled on Sunday that it is ready to hit back hard at sanctions threatening its economy, by announcing it has halted its limited oil sales to France and Britain.
Foreign Minister Ali Akbar Salehi said his country was keen to quickly resume mooted talks with world powers, once a place and date were agreed.
The last talks collapsed in Istanbul in January 2011, but Tehran has responded positively to an EU offer to look at reviving them.
"We are looking for a mechanism for a solution for the nuclear issue in a way that it is win-win for both sides," Salehi said.
But he added that Iran remained prepared for a "worst-case scenario."
Such a scenario -- war -- remained very much the subtext of a Sunday visit to Israel by US National Security Adviser Tom Donilon.
Israel has been gripped by speculation that it is closer to mounting a pre-emptive strike on Iran's nuclear programme, although it has denied reaching such a decision.
The United States, while not ruling out its own possible military option against Iran, appeared to be holding back its main Middle East ally.
"I think it would be premature to exclusively decide that the time for a military option was upon us," the chairman of the US Joint Chiefs of Staff, General Martin Dempsey, told CNN.
"The US government is confident that the Israelis understand our concerns," The Jerusalem Post newspaper quoted Dempsey as telling CNN.
British Foreign Secretary William Hague warned on the BBC on Sunday: "I don't think the wise thing at this moment is for Israel to launch a military attack on Iran."
Israeli calculations will take into account a Wednesday announcement by President Mahmoud Ahmadinejad that Iranian scientists are boosting uranium enrichment by adding 3,000 more centrifuges to a facility at Natanz.
Iran also appeared to be about to install thousands of new centrifuges in another, heavily fortified enrichment facility near Qom, a diplomat accredited to the UN nuclear watchdog told the BBC.
Iran says the enrichment is part of a purely peaceful civilian nuclear programme.
Western nations and Israel, though, fear it is part of a drive to develop the ability to make atomic weapons.
A November report by the UN nuclear watchdog the International Atomic Energy Agency strongly suggested Iran's programme included nuclear weapons research.
The IAEA delegation due in Tehran on Monday is to hold two days of talks with officials after a previous visit at the end of January yielded no breakthrough.
"Importantly we hope for some concrete results from this trip... This is of course a very complex issue that may take a while," IAEA chief inspector Herman Nackaerts told reporters in Vienna before leaving for Iran.
Mark Fitzpatrick of the London-based International Institute for Strategic Studies told AFP he was not optimistic.
He said this was "because I think any honest answers to the IAEA's questions would confirm that Iran had been involved in weapons-related development work and Iran wouldn't want to admit that for fear of being penalised."
The West has ramped up its economic sanctions on Iran in an effort to force it to halt the enrichment.
"But so far they haven't worked and we've been seeing a regime that breaks all the rules," Israeli Prime Minister Benjamin Netanyahu said on Thursday.
Iran on Sunday underlined its defiance by declaring that no more crude was being exported to France and Britain, in retaliation for an EU-wide ban on its oil that will come into full effect from July 1.
Meanwhile, Iran and Israel have shown a willingness to tangle, at least covertly.
Bomb plots to kill Israeli diplomats in India, Georgia and Thailand emerged on February 13 and 14, using similar methods to those in the murders of Iranian nuclear scientists in the past two years attributed to Israeli agents.
Iran denied any involvement in the plots against the Israeli diplomats -- one of whom was gravely wounded when her car was targeted in New Delhi. Israel has neither confirmed nor denied being behind the Tehran hits.
Both countries have also made preparations for open conflict.
Israel in 2009 reportedly purchased 55 US bunker-busting bombs, and this year called off its biggest-ever joint military manoeuvres with the United States that were scheduled for around now.
Iran has been conducting manoeuvres -- the most recent, land-based ones announced on Sunday in central Iran -- and flaunting its ballistic and cruise missiles.
Two Iranian warships also entered the Mediterranean at the weekend, and were within striking distance of Israel where the military said it would deploy a battery of "Iron Dome" rocket interceptors in the Tel Aviv area from Monday.