ZAVIDOVO (Russia), March 4 - The format of Ukraine's cooperation with the countries of the Customs Union should be determined at four-party talks between all member states, President Viktor Yanukovych said.

"The format of work with the Customs Union should be determined at four-party talks," Yanukovych said at a meeting with Russian President Vladimir Putin in Zavidovo (Tver region) on Monday.

At the same time, Yanukovych said that Ukraine understands that Russia plays a key role in the Customs Union.