During a visit earlier by the foreign ministers of Britain, France and Germany, Iran stepped back from the brink of confrontation with the international community over its nuclear programme -- vowing "full transparency" to the IAEA and promising that atomic weapons have no part in its defence doctrine.
The United States -- whose always taut relations with Teheran were strained further when President George W. Bush included the Islamic Republic in his "axis of evil" -- gave a cautious welcome to the breakthrough, describing it as a "positive step."
Analysts said the intervention of Jack Straw, Dominique de Villepin and Joschka Fischer was an example of how European diplomacy could be used to build on -- not compete with -- Washington's and could go far to repair trans-Atlantic bridges damaged in the war over Iraq.
"This is the arrival of Europe on the international scene and in the Middle East in a role that complements that of the US," said Dominique Moisi of the French Institute of International Relations (IFRI).
Europe's softly-softly method of operating contrasted with Washington's more direct approach, he said, but what had happened proved that the two could exist side-by-side.
"Here we see Europe moving ahead on a really urgent issue not against the US but beside the US. The US could not reach a deal like this with Iranians, but that does not mean they were not on more or less the same wave-length as the Europeans," Moisi said.
"The episode shows that when the big three get together they can make a real difference ... This will help repair the spectacular divisons caused by the war in Iraq which showed up the price to be paid when Europe does not make itself felt," he said.
According to Middle East specialist Pierre-Marie de la Gorce, "European governments had every reason to think that the US would be unable to make the right gestures to get Iran to accept these (IAEA) controls."
Washington also does not have diplomatic relations with Tehran.
"Only the Europeans could do it because for the last 25 years the Americans have been conditioned by the idea of vengeance against the Iranians who humiliated them in the 1979 hostage crisis," said Georges Le Guelte, a former member of the IAEA's governing board.
"It is a really remarkable success because it is so intelligent. The ministers gave the Iranians a pretext to give way but at the same time added assurances that allowed them to save face," he said.
And Le Guelte said the diplomatic achievement -- won by the EU's three core nations -- was a lesson for future European action.
"It shows that while in the EU it may be impossible for 15 or 25 countries to act, the three at the heart can do all sorts of things. If we had had to wait for the 15 (currrent members) to agree on Iran we would still be waiting. This shows the course we have to follow," he said.