Chemical weapons inspectors are expected to be allowed to visit the site of the alleged gas attack in Syria on Wednesday.
It comes after Russia was accused of preventing inspectors for the Organisation for the Prohibition of Chemical Weapons (OPCW) reaching the site where 75 people were thought to have died in the rebel-held town of Douma.
But Russian officials at OPCW headquarters in The Hague have said arrangements are being made for the inspectors to travel to the site.
However, there are fears in Western capitals that - more than a week on - much of the evidence of what happened on April 7 will no longer be there.
Meanwhile MPs are to stage a second emergency debate in the space of 24 hours over Britain's role in missile strikes on Syria's chemical warfare facilities.
Commons Speaker John Bercow granted Labour leader Jeremy Corbyn a debate to consider the rights of Parliament to debate and approve military action by British forces overseas. The session is expected to begin on Tuesday afternoon.
It follows a marathon three-hour Commons statement by Theresa May on Monday which was then followed by another three-hour debate on a backbench motion.
The "take note" motion, saying the House had considered the situation in Syria and the Government's approach passed comfortably by 314 to 36 in a largely symbolic vote, with Labour abstaining.
In the course of her appearance at the Despatch Box, the Prime Minister largely succeeded in placating Conservative critics - despite some concerns among some backbenchers that there was no Commons vote.
She even won support from a series of Labour MPs who backed her decision to join the US and France in mounting strikes.
Mr Corbyn - who repeated his assertion that the action was "legally questionable" - faced jeers from Tory MPs after telling Mrs May she was "accountable to this Parliament, not to the whims of the US president".
The prime minister, however, defended her decision not to recall Parliament, saying speed had been "essential", suggesting the "security" of the operation could have otherwise been compromised.
Russia, the Syrian regime's principle backer, has insisted there is no proof that chemical weapons had even been used in Douma.
In the wake of the furious row over the poisoning of former double agent Sergei Skripal and his daughter, Yulia, in Salisbury, Russian foreign minister Sergey Lavrov said East-West relations were now worse than they were at the time of the Cold War.
Meanwhile the UK and US have issued an unprecedented joint alert on the threat of "malicious cyber activity" by the Russian state.
Britain's National Cyber Security Centre (NCSC) combined with the FBI and the US Department of Homeland Security to say Kremlin actions threaten "our respective safety, security and economic well-being".
Officials said "millions" of computers worldwide had been targeted in operations designed to "support espionage...and potentially lay a foundation for future offensive operations".