LONDON

The Polish prime minister on Sunday reiterated readiness to work on a 28-point US peace plan for Ukraine but questioned who authored it amid claims that it favors Russia. Secretary of State Marco Rubio, however, has insisted it was drafted by the US.

"Together with the leaders of Europe, Canada and Japan, we have declared our readiness to work on the 28-point plan despite some reservations," Donald Tusk wrote on US social media company X.

"However, before we start our work, it would be good to know for sure who is the author of the plan and where was it created."

In a joint statement on Saturday, the leaders of Germany, France, the UK, Italy, Spain, Finland, the Netherlands, Ireland, Norway, Canada, and Japan as well as the presidents of the European Council and European Commissions said the plan could be a basis for talks to end the war but the draft "will require additional work."

"We are clear on the principle that borders must not be changed by force," the statement said, and expressed concern over proposed limits on Ukraine's army.

While a group of US senators branded the plan a Russian "wish list," Rubio said it was "authored" by the US and has been put on table as a "strong framework for ongoing negotiations."

"It is based on input from the Russian side. But it is also based on previous and ongoing input from Ukraine," he said on US social media company X.

The draft appears to require Ukraine to surrender additional territory to Russia, limit the size of its military, and formally abandon its bid to join NATO. President Donald Trump has given his Ukrainian counterpart Volodymyr Zelenskyy until Thursday to respond.

Zelenskyy, who authorized a delegation for talks on the plan in Switzerland, said he faces a tough choice, namely the "loss of our dignity or the risk of losing a key partner."

Russia started its "special military operation" in February 2022 for what it calls the "denazification" and "demilitarization" of Ukraine. Besides limits on the Ukrainian military and barring NATO membership, Moscow wants the Russian language to enjoy official status in Ukraine.