GENEVA (AP) ― World powers share a belief that Syria could descend into civil war and plan to map out possible ways to avoid such a disaster for the region, a deputy to international envoy Kofi Annan said Wednesday.

Jean-Marie Guehenno told reporters after privately briefing the U.N. Security Council, the world body’s most powerful unit, that diplomats are deeply troubled by Syria’s cycle of violence.

“I believe that in the council there’s an understanding that any sliding toward full-scale civil war in Syria would be catastrophic, and the security council now needs to have that kind of strategic discussion on how that needs to be avoided,” Guehenno said in Geneva after speaking to the New York-based Security Council by videoconference.

However, there was no indication that Russia, one of the veto-wielding permanent members of the Security Council, was changing it’s position on Syria.

Dmitry Peskov, President Vladimir Putin’s spokesman, was quoted as saying by the ITAR-Tass news agency Wednesday that “there can be no talk” about a shift in Russia’s stance on Syria under foreign pressure.

Russia, along with China, has twice shielded Syrian President Bashar Assad’s regime from the U.N. sanctions over his crackdown on protests. Syria is Russia’s last ally in the region, providing Moscow with its only naval base outside the former Soviet Union and a top customer for Russian weapons industries.

Guehenno, the Annan deputy and a former U.N. peacekeeping chief, also warned of the possibility of outside groups and terrorists taking advantage of the violence. “In any situation where there is a risk of civil war you have opportunistic actors, if one can say that, that can try to exploit that,” he said.

Guehenno said he told the closed session of the 15-nation council that Annan’s six-point peace plan to end the 15-month conflict must be fully implemented and that political process must include talks between the Syrian government and the opposition.

“It’s very important that the Security Council be united in pushing for a political process,” Guehenno said.

Annan held talks with Assad in Damascus on Tuesday following the weekend massacre in Houla of more than 100 people, many of them women and children.

At the U.N. headquarters in New York, Germany’s U.N. Ambassador Peter Wittig said Guehenno told the council that while Annan was in Damascus he appealed to Assad’s government “to take bold steps forward” to end to end the violence immediately and implement the peace plan.

U.S. Ambassador Susan Rice said the worst but most probable scenario in Syria is a failure of Annan’s peace plan and a spreading conflict that creates “a major crisis” not only in Syria but also region-wide.

“And members of this council and members of the international community are left with the option only of considering whether they are prepared to take actions outside of the Annan plan and the authority of this council,” she told reporters.

The best scenario would be for the Syrian government to immediately start complying with the plan, she said, but that doesn’t seem to be “a high probability.”

And if Assad refuses to implement it, Rice added, then the Security Council should set aside its differences and up the pressure on Syria with added sanctions.

Minutes after she spoke, Russia’s U.N, Ambassador Vitaly Churkin told reporters that “our attitude to sanctions frankly continues to be negative.”

But Rice, Churkin and other council members agree the best scenario is full implementation of the Annan plan, with talks between opposing sides, despite the increasing worry that will never happen.

They also agree on the need for all sides to immediately halt the violence and for Syrian troops and heavy weapons to be withdrawn from towns and cities, with the government also providing access to detainees, journalists and humanitarian workers.

Annan said in Damascus that the situation has reached “a tipping point” and many council ambassadors agreed, including Rice.

“I think we may be beginning to see the wheels coming off this bus,” she said.

Britain’s U.N. Ambassador Mark Lyall Grant said Guehenno and one of his French successors, the current U.N. peacekeeping chief Herve Ladsous, provided a grim briefing.

Lyall Grant said there was a sense of “revulsion” at the weekend massacre and the increase in extremist attacks with a new sectarian element, all of which are throwing up roadblocks to Annan’s peace plan.