The Trump administration said Tuesday that it is consulting with Congress about additional sanctions on Russia over the poisoning of an ex-Russian spy in Britain, in a move that is likely to further strain already tense relations.

The State Department said in a statement that Russia has failed to meet a 90-day deadline that fell on Tuesday to comply with a 1991 U.S. law on preventing the use of chemical weapons.

The United States and its allies have accused the Russian government of involvement in the March nerve agent attack on Sergei Skripal and his daughter in the English city of Salisbury. The State Department determined in August that Russia violated the chemicals law in the Skripal case. Moscow strongly denies that it was behind the attack.

Department spokeswoman Heather Nauert said in a statement that the agency will now consult Congress on the fresh sanctions.

“We intend to proceed in accordance with the terms of the CBW Act, which directs the implementation of additional sanctions,” she said, referring to Biological Weapons Control and Warfare Elimination Act.

Ties between Moscow and Washington are at Cold War lows despite President Donald Trump’s hopes of building closer ties with Russian President Vladimir Putin. Russia already faces U.S. sanctions over its alleged interference in the 2016 U.S. election and its actions in Ukraine.

Putin has said Russia had no reason to attack Skripal, who had served time in prison for spying for Britain and then was released in a spy swap deal in 2010. Moscow also denies meddling in U.S. politics.

According to the credit agency Standard & Poor’s, the Trump administration will be choosing three of the following six options for sanctions: restricting U.S. imports of Russian oil, banning U.S. technology and food exports, restricting Russia’s access to international financial markets, prohibiting U.S. banks from giving loans to the Russian government, further downgrading diplomatic ties and restricting travel in the U.S. by Russia’s Aeroflot airlines.

Rep. Ed Royce, the Republican chair of the House Foreign Affairs Committee, called on the Trump administration “to act quickly” on sanctions.

In September, Britain charged two Russian citizens with trying to kill Skripal and his daughter, Yulia, with the Soviet-designed nerve agent Novichok. The Skripals survived the attack, but spent weeks in the hospital.

Britain says “the operation was almost certainly approved at a senior government level.”

British-based investigative group Bellingcat has identified the two suspects as members of the Russian military intelligence unit known as GRU, one a military doctor and the other, a decorated agent.

The men deny involvement, saying they traveled to Salisbury as tourists.

(AP)