Russia blocks monitoring of more Ukraine border checkpoints - U.S.

VIENNA (Reuters) - Russia has refused to increase international monitoring of the border with Ukraine, the United States said on Wednesday, after European security watchdog OSCE extended its observers' existing mandate at two checkpoints by a month.

Ukraine and the West have accused Russia of sending weapons and soldiers to help pro-Russian separatists in the country's east, a charge Moscow denies. More than 3,700 people have been killed in fighting since April in eastern Ukraine.

Senior U.S. official Jennifer Bosworth, speaking at a meeting of the Organisation for Security and Cooperation in Europe, accused Russia of "undue restrictions" of the 16 OSCE observers and three administrative staff, whose three-month mandate was due to end in late October.

"We are concerned that ... the mission will be unable to monitor the extent to which Russia is participating in or facilitating the flow of illegal arms, funding, and personnel to support the separatists in eastern Ukraine," she said.

There was no immediate comment from Russia's mission to the 57-nation body, which takes decisions by consensus.

Kiev and the rebels reached a ceasefire agreement in early September. But the United Nations this month said the conflict was still claiming about 10 lives a day.

The OSCE said its member states decided to extend the mandate of the observer mission at the Russian checkpoints Gukovo and Donetsk until Nov. 23. They will continue to report on movements across the Russian-Ukrainian border, it said.

Bosworth said it was "deeply regrettable" that Russia would not agree to expand the OSCE's monitoring work on the border.

"We once again have to accept a limited-scope mission, covering just two border checkpoints - which account for approximately one kilometre (0.6 miles) of the 2,300 kilometre border," she said in a statement.

The OSCE also operates a separate, larger monitoring mission in Ukraine itself with 250 international observers seeking to reduce tensions and report on the situation on the ground. That mission has a mandate running until March next year.

The U.S. statement said other OSCE members had also asked for a bigger scope for the mission, but gave no details.

(Reporting by Fredrik Dahl; Editing by Louise Ireland)