UPDATE1: China, Russia veto Western-backed U.N. resolution on Syria.

NEW YORK, July 19 Kyodo

(EDS: ADDING QUOTES, MORE INFO)

Russia and China vetoed a Western-backed U.N. Security Council resolution Thursday that threatened new sanctions against Syria.

Backed by five countries, the resolution called for extending the U.N. Supervision Mission in Syria by 45 days, while demanding Damascus cease using heavy weapons in populated areas and pull troops from such areas. The mission's mandate is set to expire midnight Friday.

The resolution stated that if the Syrian authorities have not fully complied with their earlier agreed commitments within 10 days, the council will impose nonmilitary sanctions.

"It's pitiful and deeply regrettable that again today Russia and China, for the third time, have vetoed a resolution that garnered the overwhelming support of this Security Council," U.S. Ambassador to the United Nations Susan Rice told reporters after the votes were cast.

"What this resolution would have done was to provide the political support to the U.N. mission that might have given it a fighting chance to accomplish its mandate."

Russia, as an ally of Syria, along with China has previously vetoed two separate resolutions calling for tougher measures against Syrian President Bashar al-Assad .

Any of the five permanent council members -- Britain, China, France, Russia and the United States -- can exercise a veto that would block the passage of any resolution.

South Africa and Pakistan abstained from voting Thursday.

Kofi Annan, the special envoy for the Syrian crisis, has repeatedly called on the 15-member council to act in unity to press for a cessation of violence so that a political transition could begin.

"Now it is obvious that the international community is divided, so we are going to see if something is still possible on the diplomatic front," French Ambassador Gerard Araud told reporters, stressing how the western draft carried out what Annan had called for.

In a statement released from Geneva, Annan was "disappointed that at this critical stage the U.N. Security Council could not unite and take the strong and concerted action."

"The sponsors of the just-blocked draft resolution were well aware that it simply stood no chance of being adopted," Russian Ambassador Vitaly Churkin said in his statement.

He added that Moscow "cannot accept a document...which would open the path for pressure of sanctions and further to external military involvement in Syrian domestic affairs."

Rice countered in her statement stressing that the western resolution "would in no way authorize nor even pave the way for foreign military intervention."

Beyond the issue of the threat of sanctions, there are also apparent divisions in how the mandate of UNSMIS remains to be carried out.

The British in their latest draft resolution proposed a final extension for 30 days and a "willingness" to renew the mandate if there was a sufficient reduction of violence to allow the observers to carry out their work.

An alternative text drafted by Pakistan called for a technical rollover for 45 days.

Three hundred unarmed military observers had been deployed in Syria to try to ensure that the government and opposition forces were respecting a cease-fire, which has not been kept.

In light of increasing safety concerns for the observers, their mission has been dramatically scaled back and there have been disagreements among council members about its effectiveness as the midnight deadline approaches.

So far more than 10,000 have died in the 16-month conflict since Assad's regime cracked down on protesters who took to the streets during the Arab Spring last year.