U.S. Secretary of State Antony Blinken and Russian Foreign Minister Sergei Lavrov had a testy exchange over Ukraine at a dinner with dozens of their colleagues this week, according to people familiar with the discussions.

The verbal tension erupted as the U.S. and its European allies seek ways — including possible sanctions — to counter the threat of a Russian invasion of Ukraine after President Vladimir Putin’s troop buildup on the neighboring country’s border.

Lavrov took the floor at the Organization for Security and Cooperation in Europe dinner in Stockholm on Dec. 1 to revisit Russia’s view that the collapse of a pro-Moscow administration in Ukraine in 2014 was a coup, according to two of the people. He also alleged that the North Atlantic Treaty Organization and the European Union were suppressing dissent and threatening Russia.