"We are firm on the principle that borders should not be changed by force. We are also concerned about the proposed restrictions on the Ukrainian armed forces, which would make Ukraine vulnerable to future attacks," they said in a joint statement.

The text was signed by the leaders of Great Britain, France, Germany, Italy, Spain, the Netherlands, Ireland, Finland, Norway and the European Union, as well as the prime ministers of Canada and Japan.

It was issued after an emergency meeting on the sidelines of the G20 summit in Johannesburg in response to the plan promoted by the US.

The leaders said they"welcome the United States' continued efforts to achieve peace in Ukraine" and believe the US 28-point plan "includes important elements" to achieve this goal.

"Therefore, we believe that this project is a foundation that will require additional work," the statement said.

It stressed that"the implementation of the elements relevant to the European Union and NATO will require the consent of the EU and NATO member states, respectively."

"We are ready to engage to ensure sustainable peace in the future," the statement said.

Washington has reportedly proposed a plan to end the war in Ukraine, which appears to be based largely on Russian demands. It includes not only the retention of the occupied territories under Russian control, but also Ukraine's commitment not to join NATO, not to expand the alliance, and Russia's return to the G8, according to a draft of the plan obtained by AFP.