* "Never said when attack on Syria would take place" - Trump
* Russian military enters town hit by alleged gas weapon
* Moscow says crisis hotline with Washington is in use
* Russia cites "dishonest accusations", wants no escalation
* Western action would threaten international peace - Assad
* Russian ships reported to leave Syria naval base
US President Donald Trump cast doubt on Thursday over the timing of his threatened strike on Syria in response to a reported poison gas attack, while France said it had proof of Syria's guilt but needed to gather more information.
Fears of confrontation between Russia and the West have been running high since Trump said on Wednesday that missiles "will be coming" after the suspected chemical weapons assault in the Syrian town of Douma on April 7, and lambasted Moscow for standing by Syrian President Bashar al-Assad.
"Never said when an attack on Syria would take place. Could be very soon or not so soon at all!" the US president said in his latest early morning tweet on Thursday.
French President Emmanuel Macron said France has proof the Syrian government carried out the attack, which aid groups have said killed dozens of people, and will decide whether to strike back when all the necessary information has been gathered.
"We have proof that last week ... chemical weapons were used, at least with chlorine, and that they were used by the regime of Bashar al-Assad," Macron said, without offering details of any evidence.
"We will need to take decisions in due course, when we judge it most useful and effective," he told broadcaster TF1.
Prime Minister Theresa May prepared to convene a special cabinet meeting at 1430 GMT to weigh whether Britain should join the United States and France in a possible military action.
May recalled ministers from their Easter holiday to debate action over what she has cast as a barbaric poison gas attack in Douma, then rebel-held, just east of the capital Damascus.
There were signs, though, of a global effort to head off a direct confrontation between Russia and the West. The Kremlin said a crisis communications link with the United States, created to avoid an accidental clash over Syria, was in use.
"The situation in Syria is horrific, the use of chemical weapons is something the world has to prevent," Britain's Brexit minister David Davis said.
"But also it's a very, very delicate circumstance and we've got to make this judgment on a very careful, very deliberate, very well thought-through basis."
There was no direct word from Russian President Vladimir Putin on the crisis, though he discussed the situation with Turkish President Tayyip Erdogan by phone on Thursday, Interfax news agency said.
The Russian Foreign Ministry said Moscow sought no escalation of the situation, but that it could not support "dishonest accusations" and it had found no evidence of a chemical weapons attack in Douma.
Statements from Washington have been militaristic, ministry spokeswoman Maria Zakharova said, and threats by the United States and France were a violation of the UN charter.
Syria's military has repositioned some air assets to avoid missile strikes, US officials told Reuters. Locating them alongside Russian military hardware might make Washington reluctant to hit them.
Russian ships had left the Tartus naval base in Syria, Interfax news agency quoted a Russian lawmaker as saying. Vladimir Shamanov, who chairs the defence committee of the lower house, said the vessels had departed the Mediterranean base for their own safety, which was "normal practice" when there were threats of attack.
For its part, the Russian military said it had observed movements of U.S. Navy forces in the Gulf. Any US strike would probably involve the navy, given the risk to aircraft from Russian and Syrian air defences. A US guided-missile destroyer, the USS Donald Cook, is in the Mediterranean.
Moscow's ambassador to Lebanon, Alexander Zasypkin, warned on Wednesday that any US missiles unleashed at Syria would be shot down and the launch sites targeted.
Russia, Assad's most important ally in his seven-year-old war with rebels, said it had deployed military police in Douma on Thursday after the town was taken over by government forces.
"They are the guarantors of law and order in the town," RIA news agency quoted Russia's defence ministry as saying.
Assad said any Western action "will contribute nothing but an increase in instability in the region, threatening international peace and security", Syrian state TV reported.
The Syrian conflict has increasingly widened the rifts between Moscow, Washington and European powers and inflamed the bitter rivalries that run across the Middle East.
Syria, Russia and Iran say reports of the attack were fabricated by rebels and rescue workers in Douma and have accused the United States of seeking to use it as a pretext to attack the government.
Nervous world stock markets showed signs of recovery after Trump signalled military strikes might not be imminent.
Israeli air strike
Syria and its allies Russia and Iran say Israel was behind an air strike on a Syrian air base on Monday that killed seven Iranian military personnel, something Israel has neither confirmed nor denied.
Russia's Putin spoke to Israeli Prime Minister Benjamin Netanyahu by phone on Wednesday and urged him to do nothing to destabilise Syria. Netanyahu's office said: "The prime minister reiterated that Israel will not allow Iran to establish a military presence in Syria."
Ali Akbar Velayati, a top adviser to Iran's Supreme Leader Ali Khamenei, said the Western threats were "based on lies" about the poison gas assault, after meeting Assad. He said later he hoped Syria's army and its allies would drive US troops out of eastern Syria, and take Idlib in the northwest from rebels.
May has ordered British submarines to move within missile range of Syria in readiness for strikes against the Syrian military that could begin as early as Thursday night, London's Daily Telegraph newspaper said on Wednesday.
The BBC reported that May was ready to give the go-ahead for Britain to take part in military action. She would not seek approval from parliament, the BBC said.
Opposition Labour leader Jeremy Corbyn said parliament must be consulted.
Parliament voted down British military action against Assad's government in 2013 in an embarrassment for May's predecessor, David Cameron. That then deterred the US administration of Barack Obama from similar action.