The "strength of the support" shown to the UK over the poisoning of former Russian agent Sergei Skripal and his daughter has been encouraging, the foreign secretary has said, BBC reports.
Boris Johnson said the UK had been talking to friends and there had been a "willingness" to show "solidarity".
Russia's foreign minister said claims of Russian involvement were "rubbish".
The UK has given Russia a midnight deadline to explain why a Russian-made nerve agent was used in the attack.
Russian Foreign Minister Sergei Lavrov said that Russia had been refused access to the substance that was used to poison Mr Skripal and it would not respond to the ultimatum until it was given access.
The UK ambassador to Russia, Laurie Bristow, has been summoned to the Russian Foreign Ministry, according to Russian news agency Interfax.