Russia said Sunday that the United States has denied visas to journalists who wanted to cover Foreign Minister Sergey Lavrov’s trip to New York, and Lavrov suggested that Moscow would take strong retaliatory measures.

There was no immediate comment from the U.S. State Department about the claim of refused visas. “The United States takes seriously its obligations as host country of the U.N. under the U.N. Headquarters Agreement, including with respect to visa issuance,” a State Department spokesperson said in a statement.

The journalists aimed to cover Lavrov’s appearance at the United Nations to mark Russia’s chairmanship of the Security Council.

“A country that calls itself the strongest, smartest, free and fair country has chickened out and done something stupid by showing what its sworn assurances about protecting freedom of speech and access to information are really worth,” Lavrov said before leaving Moscow on Sunday.

“Be sure that we will not forget and will not forgive,” he said.

“I emphasize that we will find ways to respond to this, so that the Americans will remember for a long time not to do this,” Deputy Foreign Minister Sergei Ryabkov said.

The dispute comes in the wake of high tensions with Washington over the arrest last month of Wall Street Journal reporter Evan Gershkovich, whom Russia accuses of espionage. The United States has declared him to be “wrongfully detained.”

Many Western journalists stationed in Moscow left the country after Russia sent troops into Ukraine. Russia currently requires foreign journalists to renew their visas and accreditation every three months, compared to once a year before the fighting began.