Syria's government still has chemical weapons capacity, Turkey's Foreign Minister says, and he's called for measures to prevent it being used.
Turkish Foreign Minister Mevlut Cavusoglu said his country's investigations showed the risk of chemical weapons would continue as long as Syrian President Bashar al-Assad remains in power.
His comments came as G7 foreign ministers attempt to agree a common position on the Syrian conflict, before US secretary of state Rex Tillerson flies to Russia to try to persuade it to abandon its Syrian ally.
Their meeting in Italy follows last week's apparent chemical attack on the rebel-held Syrian town of Khan Sheikhoun.
Syria has denied it used chemical weapons in the attack, which left 89 people dead, claiming the chemicals involved were from rebel warehouses.
Reports overnight quoted a senior US official as saying Russia knew of the chemical attack because a drone had been flying over a hospital in Khan Sheikhoun as victims sought help.
Hours later a jet bombed the hospital in what the US believed was an attempt to cover up the attack, the Associated Press reported.
After the attack, the US launched 59 missiles at a Syrian government air base.
The UK has suggested threatening tightly focused sanctions on Russian and Syrian military officers.
Downing Street says that when US President Donald Trump and the British Prime Minister Theresa May talked on the phone on Monday night, they agreed a window of opportunity existed to persuade Russia its alliance with Assad was no longer in its strategic interest.
The problem for them remains that Russian President Vladimir Putin has never accepted that before, and still shows no sign at all of changing his position, a BBC correspondent said.
Russia is already subject to a raft of sanctions imposed by the US and EU in response to the annexation of Crimea and the crisis in eastern Ukraine.
Russia and Iran, Mr Assad's key military backers, are also threatening retaliation if there are any further American air strikes, saying the US attack had crossed "red lines".
"From now on we will respond with force to any aggressor or any breach of red lines from whoever it is and America knows our ability to respond well," said a statement from a joint command centre comprising the forces of President Assad's allies.
In a sign of the tensions between the US and Russia, the Kremlin has said that Mr Tillerson will not meet President Vladimir Putin when he visits Moscow on Tuesday.
Sticking to protocol, he will hold talks with his Russian counterpart, Sergei Lavrov. While he has known Mr Putin for years, Mr Tillerson will be the first US secretary of state not to meet the top Russian leader on a first trip to Moscow.
North Korea responds to US fleet movements
North Korea has said it will defend itself "by powerful force of arms" in response to the US deployment of a Navy strike group to the Korean peninsula.
The foreign ministry, quoted by state news agency KCNA, said the deployment showed "reckless moves for invading" had "reached a serious phase".
The US Pacific Command said the move was aimed at maintaining readiness in the region. The move came after the North Korean administration weighed in on the US attack on the Syrian air base, and after a succesful test of four missiles.
North Korea has carried out tests to develop a nuclear missile. The UN has banned it from missile or nuclear tests but Pyongyang has repeatedly broken those sanctions.
Mr Trump has said the US is prepared to act alone to deal with the nuclear threat from North Korea.
- Reuters / BBC