* U.S. wants international monitors to be sent to Ukraine
* Sees "loud chorus of support" during OSCE meeting
VIENNA, March 2 (Reuters) - The United States has won tentative support from many members of the OSCE, Europe's main human rights and democracy watchdog, for an OSCE monitoring mission to be sent to Ukraine to help defuse the crisis there, its envoy said on Sunday.
The 57-nation Organization for Security and Cooperation in Europe's discussed the situation in Ukraine during an informal extraordinary session on Sunday evening to prepare for a meeting of its Permanent Council in Vienna on Monday.
Ukraine mobilised for war on Sunday and Washington threatened to isolate Russia economically after President Vladimir Putin declared he had the right to invade his neighbour, creating Moscow's biggest confrontation with the West since the Cold War.
The U.S. envoy to the OSCE said he could envisage a mission numbering in the hundreds to take stock of human rights concerns, monitor treatment of minority populations and evaluate security concerns raised by both sides of the conflict. It could also help lay the groundwork for elections.
However, such a mission would be likely to require a consensus decision, meaning Russia's support would be needed.
"I was very heartened to hear a loud chorus of support from around the room ... for the use of monitors, and indeed an openness by the Russian delegation, which didn't say a great deal today and reserved comment for tomorrow but left the door open on the topic of monitors," U.S. Ambassador Daniel Baer told reporters.
"Obviously nobody wants war and it was very clear in that room today that every delegation agreed on the need to de-escalate," he said.
The United States has already suggested that the United Nations or the OSCE - originally set up during the Cold War as a platform for dialogue between East and West - could send observers to Ukraine. Moscow has veto power at both bodies.
Baer said the Russian delegation had raised a number of concerns about the situation on the ground. "These are the kinds of concerns that have been addressed elsewhere by international monitors," Baer said.
Moscow has said Russian speakers were under threat from Ukraine's new leaders, who took over after Russian ally Viktor Yanukovich fled huge protests against his repression and rejection of a trade deal with the European Union. Ukraine says it has no intention of threatening Russian speakers.
Ambassador Thomas Graeminger of current OSCE chairman Switzerland said many delegations had referred to the possibility of launching a monitoring operation in Ukraine.
"It would make sense basically for all stakeholders to mount such an operation," he said. "It could oversee respect for human rights and for minority rights in particular."
The OSCE meeting had clearly shown that there was a "grave concern about the threat to sovereignty and territorial integrity of Ukraine", Graeminger said. (Reporting by Michael Shields and Fredrik Dahl; Editing by Kevin Liffey)