European Union countries may decide this week whether to impose new political or economic sanctions on Russia after the U.K. accused Moscow of using a nerve agent on its territory, according to a senior Polish government official.

“Poland supports the view that we should show solidarity within the EU and NATO and show Russia that it can’t cross new boundaries,” Michal Dworczyk, who heads Polish Prime Minister Mateusz Morawiecki’s office, told Radio Zet on Monday. Economic sanctions as well as expulsions of Russian diplomats by some EU nations are being considered, he said.

The comments come as Prime Minister Theresa May’s government signals that it will seek further action against President Vladimir Putin’s government after ordering 23 Russian diplomats to leave the U.K. Britain has received backing from countries including Germany and France as well as the U.S. for its position that Russia is to blame for the poisoning of a former spy and his daughter in England, the first use of a nerve agent on European soil since World War II.

Morawiecki said after a weekend phone conversation with May that Poland stood “hand-in-hand” with the U.K. “in the face of illegal and aggressive actions by Russia.” German Chancellor Angela Merkel is due in Warsaw later on Monday for talks with Morawiecki and President Andrzej Duda. EU leaders then meet for a summit in Brussels at the end of the week, when they are due to discuss the poisoning case.

The West Revives Anger at Putin, Who’s Anything But Humbled

Foreign Secretary Boris Johnson was due to brief his EU counterparts on latest developments at a regularly scheduled meeting in Brussels on Monday. Russia denies that it had anything to do with the incident.

Swedish Foreign Minister Margot Wallstrom said Johnson’s update would provide a basis for possible EU action against Russia. However, she cited the challenge the EU already faced in mustering the unanimity needed to impose and maintain economic sanctions against Russia over its encroachment in Ukraine.

‘Further Actions’

“This is an important discussion on the follow-up to all of this,” Wallstrom told reporters in Brussels Monday. “We of course know that it has not been easy always to get the unity to back up the sanctions that we already have decided on. But I think the discussion today will give a good ground for further actions. Very, very important that we are united.”

Johnson, speaking to reporters as he arrived for the meeting, said the U.K. was heartened by the level of support it was receiving.

“There’s scarcely a country around the table here in Brussels that has not been affected in recent years by some kind of malign or disruptive Russian behavior,” Johnson said. “And that is why I think the strength and the resolve of our European friends is so striking today.”