A debilitating row with Russia at UN climate talks this week exposed a fundamental flaw in how decisions are taken -- the entire system balanced precariously on an ill-defined notion of consensus, observers say.

While furious with Russia for allowing the issue to stop important work at a meeting in Bonn, negotiators agree the decision-making procedure must be clarified before any long-term damage is caused.

By tradition, decisions in the UN Framework Convention for Climate Change (UNFCCC) are made on the basis of "consensus" -- a term that implies common resolve by its 195 parties.

The principle is conceptually fuzzy and remains undefined in the organisation's rulebook, yet it was the tool that created the Kyoto Protocol and binds the community of nations to signing an ambitious new pact on carbon emissions in 2015.

"Consensus is considered important since this makes the likelihood of implementation or compliance with what has been agreed larger, and demonstrates respect for the principle of state sovereignty," Louise van Schaik of the Clingendael Institute of International Relations in the Netherlands told AFP.

But a bust-up at a low-key meeting in Germany this past week raised stark questions as to whether the practice -- at least in its current form -- can endure as the bill for climate change mounts and countries fight harder over how to apportion it.

"Since the beginning we've been sailing along in a bit of a legal grey zone where things are done by consensus without anybody really knowing what consensus means," one insider told AFP.

"It is a question of the chairs and presidents (of meetings) capturing the political will and feeding it back to delegates. Decisions are taken by acclamation -- people stand up and clap and a decision is passed. There are almost always at least one or two countries objecting."

What currently passes for consensus is traditionally achieved through frantic, late-night haggling.

Conference presidents often have to "gavel through" major deals -- declaring a decision adopted even if a country is howling dissent.

What has brought matters to a head this time is Russia, which is incensed at the way the Qatari president of last December's meeting in Doha gavelled through a decision to extend the Kyoto Protocol on curbing Earth-warming greenhouse gas emissions.

Its approval hamstrung Russia's planned sale of 5.8 billion tonnes of carbon credits amassed under the protocol's first round, which expired at the end of last year.

Outraged -- according to a well-placed source, Russian President Vladimir Putin wrote a furious letter to UN chief Ban Ki-moon -- the Kremlin is playing tough.

In the 12-day talks that finished in Bonn on Friday, Russia, backed by Ukraine and Belarus, blocked work in one of three negotiating groups -- demanding a debate on how consensus is reached.

"We have serious reasons to be concerned," Russian negotiator Oleg Shamanov told negotiators.

"If we fail to hold such a discussion on the procedural aspects of preparing and taking decisions, we may see in 2015 a situation where all efforts that have been made would be a failure."

He did not spell out how the system should be changed, but stressed it must take account of the "sovereign equality of all countries... to express their view."

Negotiators from other countries said Russia had a point and welcomed a debate on procedure.

"Our system is sick," agreed one European negotiator.

"Maybe something good can come of this -- a review of how the system works, and how it doesn't."

European Commission envoy Artur Runge-Metzger said: "Maybe this is something that also need to be explored at the UN level."

Veterans of the climate process say the problem has deep roots.

At their very first executive meeting in 1995, parties failed to adopt the UNFCCC's rules of procedure because they disagreed over Rule 42, which would allow for a vote when consensus fails.

By mutual agreement, the parties have been applying the rules ever since, but not Rule 42.

There's an irony in all this, said climate analyst Bill Hare: "Russia is one of those countries that fought for 20 years to block the adoption of rules and procedure."

Some delegates felt there was no time to wrangle over sovereign principles with just over two years left to finalise a deal that must save Earth from calamitous global warming-induced climate change.

"It's awkward and dangerous, because it could drag the plenary on, so it would impact the effectiveness of a process that already struggles to make decisions," said an NGO source.

But most agreed that, ultimately, procedural clarity would help the process as a whole.

UN climate chief Christiana Figueres described the issue as a "challenge" but also "a fantastic opportunity to be creative and to increase the efficiency of the system".

It was, however, not clear in which forum, or when, the issue will be taken up.

"Stay tuned for innovation," she said as the Bonn talks closed.