US Secretary of State Rex Tillerson embarks in Moscow today on his first round of bilateral talks with Russian officials since President Donald Trump came to power in January.
Initially, both Russia and the United States had high hopes about such meetings; as a former top oil executive, Mr Tillerson is a familiar face in the Russian capital and represents an administration committed to repairing strained relations with Russia.
But after Mr Trump ordered a missile strike on a Syrian military base last week in retaliation for what Washington and its allies say was a poisonous gas attack in which scores of Syrian civilians were killed, Mr Tillerson's best hope from today's talks is to prevent diplomatic relations with Moscow from deteriorating further.
And that won't be easy, for officials close to President Vladimir Putin - who back in 2013 personally bestowed on Mr Tillerson a top national award for his commitment to friendship between the two nations - have indicated that the Russian leader plans to cold-shoulder America's visiting top diplomat.
The war of words between Russia and the US continues unabated. Washington's attack on a Syrian airfield in the early hours of last Friday morning was an "illegitimate act of aggression" on a "sovereign country", charged Mr Vladimir Safronkov, Russia's acting United Nations envoy.
Mr Tillerson does not mince his words either. On the eve of his Moscow trip, he slammed the Russians as at best "incompetent" for allegedly allowing Syria to hold on to chemical weapons.
Meanwhile, unnamed American intelligence sources have intensified pressure on Moscow by claiming that Russian military officers in Syria knew in advance about the Damascus regime's plans to use chemical weapons against its own people, and that a hospital treating gassed victims was targeted by a "Russian-made aircraft", supposedly in order to erase incriminating evidence of the attack.
But while trading insults, both the Americans and Russians have been careful to preserve some room for diplomatic manoeuvring. Mr Tillerson has made no secret of his view that America's top priority is to defeat the Islamic State in Iraq and Syria terrorist organisation in the Middle East, rather than resolve Syria's six-year-old civil war, which he regards as a sideshow.
Russian negotiators still hope that Mr Tillerson will confirm during his talks in Moscow today that the US missile attack on Syrian installations does not represent a fundamental change in American policy in the Middle East, which has acknowledged that Syria is within Russia's sphere of influence.
And it is noteworthy that while many Russian officials have criticised the recent US actions, Mr Putin has maintained his silence. In all likelihood, he could still be persuaded to meet Mr Tillerson today, if America's top diplomat strikes a conciliatory tone. For, ultimately, Russia's best interest is served by putting this crisis behind and working for an anticipated summit between Mr Putin and Mr Trump.
The snag is that Mr Tillerson is coming under pressure from the Europeans, who see the crisis as an opportunity to persuade the US into adopting a tougher line on both Russia and the Middle East.
British Foreign Secretary Boris Johnson has cancelled his own trip to Moscow, which was due this week, and is now calling for fresh sanctions on Russia as long as the Russians maintain their support for President Assad.
And the French are joining the British in demanding a tougher approach to Russia; "the fight against terrorism cannot be effective if we don't link it to resolving the Syrian situation", said French Foreign Minister Jean-Marc Ayrault at the end of a meeting of foreign ministers from the Group of Seven industrialised nations, which Mr Tillerson attended just before flying to Moscow.
For the moment, Mr Tillerson is not ready to consider imposing further sanctions and is keen to keep communication lines with Russia.
But he needs to extract from Moscow some promise that the Russians will rein in the Syrian government and never allow another chemical attack to take place.
And the Russians themselves also have to be careful in how far they rebuff the Americans. For although they still hold the upper hand in Syria, they also know that the US and its Western allies could transform the Syrian war into a proxy conflict, thereby embroiling Russia in an Afghanistan-style confrontation that can endure for decades.
The stakes during today's negotiations are, therefore, high. And the mood is far from cordial.