Polish Prime Minister Mateusz Morawiecki said Friday the latest proposed EU sanctions against Russia were "too soft, too weak", as he visited Ukraine on the anniversary of Moscow's invasion.
In Brussels, European diplomats had hoped to announce a new package of sanctions to mark the first anniversary, but said negotiations were stalled over Poland's objections.
"As for the 10th sanctions package, we are not happy with it because it is too soft, too weak. We propose that additional people be included," Morawiecki said in Kyiv.
"We've been suggesting for a long time that additional Russian products be included," he added.
Diplomatic sources in Brussels complained that Poland's demands for tougher action were delaying the implementation of what one said was still a "very substantial" package.
The 10th round of sanctions would freeze the EU-held assets of three Russian banks, impose export controls on goods worth 11 billion euros ($11.6 billion) a year and hit Iranian drone-makers supplying Moscow.
But Poland also wants a ban on the importation from Russia of synthetic rubber that is used to make tyres, diplomats told AFP, speaking on condition of anonymity.
Italy wants a long transition period before such a ban to give its tyre industry time to find new suppliers, and the disagreement has held up a deal.
One diplomat complained that Poland's delay had "penalised Europe", since Britain and the United States had been able to announce their latest sanctions more quickly.
Lithuanian President Gitanas Nauseda also expressed concern the EU package did not go far enough.
"I always expected stronger sanctions... which would have a greater impact on Russia's economy," he told reporters on Friday.
Nauseda said he had expected sanctions to hit the Russian state nuclear energy company Rosatom.
"So far, it has not been possible to do so due to certain reservations of some countries with ties to Russia on nuclear energy," he said.
"But we are patient, and we believe that little strokes fell great oaks. This has happened in the past," he added.
Brussels had hoped to announce its sanctions late Thursday and publish details the next day, but talks broke up without agreement Friday.