WASHINGTON, March 16 - The United States said on Monday it would be ready to "increase the costs" to Russia if it fails to comply with the terms of ceasefire agreements with Ukraine, suggesting potential further economic sanctions on Moscow, Reuters reported.

In a meeting with Ukraine's finance minister Natalia Yaresko, U.S. Treasury Secretary Jack Lew said the United States would take action if Russia continued to undermine Ukraine's sovereignty and stability.

The United States last week placed sanctions on a handful of Ukrainian separatists and a Russian bank, the latest in a slew of financial penalties on Moscow and pro-Russia separatists in east Ukraine.

Meanwhile, Russia is not ready to restructure Ukraine's debt and expects Ukraine to repay the money it owes in December, Russian Finance Minister Anton Siluanov told reporters in Moscow on Monday.

"We have stated our position several times and are not changing it," Siluanov said. "We expect $3 billion in December of the current year, as was promised by the Finance Ministry of Ukraine."

His comments come after Ukraine began formal talks with private sector creditors over restructuring of its foreign debts, which is a condition of a $17.5 billion IMF loan package.

Yaresko said last week that the restructuring would include principal writedowns as well as maturity extensions and coupon reductions. She also said that Ukraine intends to treat all creditors equally.

Some investors have expressed doubts over whether a restructuring deal is possible if Russia, which holds $3 billion of Ukrainian bonds maturing in December, does not take part.

Russia has previously said that it regards Ukraine as being in violation of conditions that were agreed when Russia lent the money, in particular a clause that requires Ukraine to keep its debt below 60 percent of gross domestic product.

However, Russia has said that it does not intend to exercise its right to demand early repayment of the bonds.
Siluanov also said on Monday that Russia had not received any formal invitation to participate in debt restructuring talks. "No one has approached me personally. There have been no official letters," he said.

He said last month that Ukraine had raised the issue of restructuring with Russia in January. (rt/ez)