Britain's National Security Council will meet Wednesday to evaluate Russia's response to an ultimatum over a poisoning attack on a spy, and Prime Minister Theresa May will then unveil any "further measures", her spokesman said.
May has given Moscow until the end of Tuesday to disclose any information it has about the nerve agent attack against former Russian double agent Sergei Skripal and his daughter Yulia in the English city of Salisbury.
"There will be a meeting of the national security council tomorrow morning (Wednesday) to discuss the next steps," the spokesman said.
The council, usue made up of senior ministers and representatives of the intelligence community, would "discuss the response from Russia, whatever that may be".
May will then update parliament.
At a cabinet meeting Tuesday, May told ministers "there was no doubt of the severity of what had taken place in Salisbury, which was a reckless, indiscriminate and despicable act", her spokesman said.
"She said that Russia had been set a deadline of the end of the day to respond and if it did not do so she would return to the House on Wednesday to set out further measures."
Russian Foreign Minister Sergei Lavrov on Tuesday denied any involvement in the March 4 attack, and accused Britain of failing to honour its obligations under the international Chemical Weapons Convention.
He said Britain should have sent Moscow an official request about the substance used on its soil, but none had been received, and demanded access to the nerve agent used against Skripal.
The prime minister's spokesman responded: "The UK fully complies with all its obligations under the Chemical Weapons Convention."