Poland's President Andrzej Duda said in an interview on Sunday that the use of chemical weapons in Ukraine by Russia would be a game-changer and NATO would have to think seriously about how to respond.
Asked if the use of chemical weapons by Russian President Vladimir Putin would be a red line for NATO at which point it has to get involved, Duda told BBC television: "If he uses any weapons of mass destruction then this will be a game-changer in the whole thing."
"For sure, the North Atlantic Alliance and its leaders led by the United States will have to sit at the table and they will really have to think seriously what to do because then it starts to be dangerous."
Since President Vladimir Putin launched the Russian invasion of Ukraine on Feb. 24, the United States has been concerned that the NATO alliance should not get dragged into a wider war with Russia.
Western officials said on Friday that Russia might use chemical weapons in Ukraine in a "false flag" attack to provide a retrospective justification for its invasion, but there was nothing to suggest a broader use of such weapons in the war.
A "shocking" crossing of a line
White House National Security Adviser Jake Sullivan warned on Sunday that Russia would pay a "severe price" if it launched a chemical weapon attack on Ukraine, and said any attack on NATO territory would trigger a full response by the Western alliance.
Sullivan told CBS's "Face the Nation" that the United States and its allies were consulting closely about the increasing threat of a chemical weapons attack, and were communicating directly with Moscow to warn against any such move.
"The use of weapons of mass destruction would be a shocking additional line that (Russian President Vladimir) Putin is crossing in terms of his assault on international law and international norms," Sullivan said.
On Wednesday, Washington denied renewed Russian accusations that Washington was operating biowarfare labs in Ukraine, calling the claims "laughable" and suggesting Moscow may be laying the groundwork to use a chemical or biological weapon.
There was no immediate response from the Russian embassy in Washington to the US assertions on Wednesday.
Qatar calls to exercise restraint
Qatar's foreign minister called on all parties to "exercise restraint" and to avoid further escalation over Ukraine in a phone call with his Ukrainian counterpart, a Qatari foreign ministry statement said on Sunday.
Sheik Mohammed bin Abdulrahman Al Thani told Ukraine's Dmytro Kuleba that Qatar urged "all parties to exercise restraint, resolve disputes through constructive dialog and diplomatic methods, and to settle international disputes by peaceful means," the statement said.