The European Union on Monday lost a round in its battle to turn the Kyoto Protocol on global warming from a draft pact into an international treaty.
September 6 was a symbolic deadline for signatories to ratify Kyoto ahead of a major meeting, due in Buenos Aires from December 6-17.
Supporters had been desperately hoping Russia would ratify in time so that the gathering in Argentina could be the first at which Kyoto is debated as a full-fledged treaty rather than a draft agreement whose future is in doubt.
Ever since US President George W. Bush ditched Kyoto in 2001, all eyes have been on Russia, whose ratification is required under the mathematics of Kyoto's rulebook to push the agreement over the numbers threshold.
But as of Monday, Russia not only had failed to ratify - it still appeared reluctant and divided about even wanting to do, reviving fears that the complex accord to trim greenhouse-gas emissions would be consigned to limbo.
Joke Waller-Hunter, executive secretary of the UN Framework Convention on Climate Change (UNFCCC), which is Kyoto's parent treaty, played down Russia's absence from the list of ratifiers.
"There is no such thing as a formal deadline," Waller-Hunter told AFP in an interview on Friday.
"We had made some kind of calculations that, if they would deposit (their instrument of ratification at the UN in New York) on the 6th September, then the Kyoto Protocol would have entered into force on the 5th December.
"... it is unlikely that it is going to be the case, given the preparations (in Moscow) at the moment and given the fact that the Duma hasn't looked at it yet."
Waller-Hunter said she did not rule out "a decision" by Russia to ratify Kyoto and if this happened before the December meeting, "it would be, of course, a very good birthday present," referring to the 10th anniversary of the entry into force of the UNFCCC.
Kyoto's champion is the European Union, which in arduous negotiations to complete the treaty's rulebook in 2001 offered huge concessions to Australia, Canada and Russia, saving Kyoto from the scrapheap after Washington's pullout.
The ball now lies with Russian President Vladimir Putin, who must decide whether to submit the draft treaty to the Duma, the Russian parliament, for its approval.