The foreign ministers of the European Union's three biggest powers on Thursday sent a toughly worded letter to Hassan Rohani, Iran's chief nuclear negotiator, warning that resuming potentially arms-related nuclear work "would bring the negotiating process to an end", an EU diplomat quoted the letter as saying.
"The consequences could only be negative for Iran," it said.
British Prime Minister Tony Blair spelled out the potential consequences, telling reporters: "We certainly will support referral to the United Nations Security Council if Iran breaches its obligations and undertakings."
The letter, which was also signed by EU foreign policy chief Javier Solana, proposed ministerial level talks between the Iranians and Europeans within the next two weeks to break the impasse and avoid a crisis, the diplomat said.
"We certainly will support referral to the United Nations Security Council if Iran breaches its obligations and undertakings"
British Prime Minister Tony Blair
Earlier on Thursday, Iran vowed to resume nuclear activities, refuting suggestions it was considering, under European pressure, backing away from its threat to immediately end its freeze on uranium conversion.
Rohani said on Thursday Tehran would resume some nuclear activities because it could not continue nuclear negotiations with Europeans.
Iranian journalist Muhammad Sadiq al-Hussaini told Aljazeera Iran's resumption of its nuclear programme would serve as a warning to the European tripartite negotiating delegation to not give in to US pressure to abandon talks.
The new EU warning, however, may have had an immediate effect.
Officials close to the talks said Tehran might give talks with the EU one last chance rather than go ahead with plans to break UN seals and restart part of its nuclear fuel programme.