US, British and French missile strikes on Syria had a limited impact on Syrian president Bashar al-Assad’s ability to carry out chemical weapons attacks, US assessments have reportedly shown.

Donald Trump tweeted “Mission Accomplished” after the attacks, which members of his administration claimed had struck the heart of the country’s chemical weapons programme.

His comments echoed those made by his predecessor George W Bush in 2001 after the US ousted Iraqi dictator Saddam Hussein.

The US, Britain and France destroyed three targets tied to Syria’s weapons programme, the most important of which was the Barzah Research and Development Centre.

US intelligence concluded it was involved in the production and testing of chemical and biological warfare technology.

But four US officials told Reuters that currently available intelligence indicated Syria’s stockpiles of chemicals and precursors were believed to be scattered far beyond those three targets.

It suggested that some of it was stored in schools and civilian apartment buildings, which one of the officials referred to as “human shields”.

Speaking to Congress a day before the strikes, the US defence secretary James Mattis acknowledged one of his top priorities in crafting the operation would be to minimise the loss of life to civilians.

Syria air strikes: US, UK and France joint military action Show all 21 1 /21 Syria air strikes: US, UK and France joint military action Syria air strikes: US, UK and France joint military action A picture released by the French Defence audiovisual communication and production unit (ECPAD) shows the launching of a cruise missile from a French military vessel in the Mediterranean sea towards targets in Syria overnight. The United States, France and Britain carried out a wave of punitive strikes against Bashar al-Assad's Syrian regime in the early hours of April 14 in response to alleged chemical weapons attacks. AFP/Getty Syria air strikes: US, UK and France joint military action Rafale warplanes being prepared for take off at the Saint-Dizier aerial military base, eastern France. Media reports state that the United States, France and Britain launched military strikes in Syria to punish President Bashar Assad for an apparent chemical attack against civilians and to deter him from doing it again. EPA Syria air strikes: US, UK and France joint military action Damascus skies erupt with missile fire as the US launches an attack on Syria targeting different parts of the capital. President Donald Trump announced airstrikes in retaliation for the country's alleged use of chemical weapons. AP Syria air strikes: US, UK and France joint military action A map show the location of the air strikes carried out by the US-led coalition in Syria overnight. US Department of Defense Syria air strikes: US, UK and France joint military action The wreckage of a building described as part of the Scientific Studies and Research Centre compound in the Barzeh district, north of Damascus. AFP/Getty Syria air strikes: US, UK and France joint military action Royal Air Force tornado jets take off in the early hours from RAF Akrotiri airbase in Cyprus to conduct air strikes in Syria. Four Tornado jets fired Storm Shadow missiles "at a military facility -- a former missile base -- some 15 miles (24 kilometres) west of Homs, where the regime is assessed to keep chemical weapon precursors," the defence ministry said in a statement. AFP/Getty Syria air strikes: US, UK and France joint military action Map of where the air strikes hit in Syria released by the Pentagon. A Syrian military statement says the US, Britain and France fired 110 missiles during a joint attack on targets in Damascus and outside. Pentagon Syria air strikes: US, UK and France joint military action A photo released on the Twitter page of Hezbollah's "Central War Media" account shows night footage of flares above Damascus seen through a night-vision device as Western strikes reportedly hit Syrian military bases and chemical research centres in and around Syria's capital. US, France, and Britain announced the joint operation. AFP/Getty Syria air strikes: US, UK and France joint military action The preliminary damage assessment of Barzah research and development centre before and after the air strikes, released by the Pentagon. Pentagon Syria air strikes: US, UK and France joint military action The preliminary damage assessment of Him Shinshar chemical weapons bunker before the air strikes. Pentagon Syria air strikes: US, UK and France joint military action The preliminary damage assessment of Him Shinshar chemical weapons bunker after the air strikes. Pentagon Syria air strikes: US, UK and France joint military action The wreckage of a building described as part of the Scientific Studies and Research Centre compound in the Barzeh district, north of Damascus. AFP/Getty Syria air strikes: US, UK and France joint military action The wreckage of a building described as part of the Scientific Studies and Research Centre compound in the Barzeh district, north of Damascus. AFP/Getty Syria air strikes: US, UK and France joint military action The wreckage of a building described as part of the Scientific Studies and Research Centre compound in the Barzeh district, north of Damascus. AFP/Getty Syria air strikes: US, UK and France joint military action The preliminary damage assessment of Him Shinshar chemical weapons storage site before and after the air strikes, released by the Pentagon. Pentagon Syria air strikes: US, UK and France joint military action The preliminary damage assessment of Him Shinshar chemical weapons storage site before the air strikes. Pentagon Syria air strikes: US, UK and France joint military action The preliminary damage assessment of Him Shinshar chemical weapons storage site after the air strikes. Pentagon Syria air strikes: US, UK and France joint military action A British military Typhoon aircraft lands at the Sovereign Base Area (SBA) of Akrotiri, a British overseas territory located ten kilometres west of the southern Cypriot port city of Limassol, following US, British and French strikes on Syria. Syrian state media slammed Western strikes on Saturday as illegal and "doomed to fail," after the US, Britain and France launched a joint operation against the Damascus.government. Huge blasts were reported around the Syrian capital, moments after the three Western governments announced they were striking Syria's chemical weapons capabilities. AFP/Getty Images Syria air strikes: US, UK and France joint military action The preliminary damage assessment of Him Shinshar chemical weapons bunker before and after the air strikes, released by the Pentagon. Pentagon Syria air strikes: US, UK and France joint military action The preliminary damage assessment of Him Shinshar chemical weapons bunker before the air strikes. Pentagon Syria air strikes: US, UK and France joint military action The preliminary damage assessment of Him Shinshar chemical weapons bunker after the air strikes. Pentagon

Both the Syrian regime and Russia deny unleashing poison gas on 7 April during their offensive on Douma, which ended with the recapture of the town, that was the last rebel stronghold near the capital, Damascus.

Attempts to investigate were thwarted and when a UN security team visited the site of the suspected attack earlier this week, they were fired on by assailants, forcing them to retreat and further delaying the fact-finding mission by experts from the international chemical weapons watchdog.

US officials said the assessment showed the strikes, particularly on Barzah, did degrade Syria’s chemical weapons capability.

But it also indicated a large quantity of chemical weapons was stored elsewhere.

While crude, it “is about as good as it needs to be for Assad’s purposes”, another official said.

Douma chemical attack: Syria war in pictures Show all 13 1 /13 Douma chemical attack: Syria war in pictures Douma chemical attack: Syria war in pictures A child receiving oxygen through respirators following an alleged poison gas attack in the rebel-held town of Douma AP Douma chemical attack: Syria war in pictures A child is treated in a hospital in Douma White Helmets Douma chemical attack: Syria war in pictures An image grab taken from a video released by the Douma City Coordination Committee shows unidentified volunteers spraying a man with water at a make-shift hospital following an alleged chemical attack AFP/Douma City Coordination Committee Douma chemical attack: Syria war in pictures People cover their faces after an alleged chemical attack in Douma EPA Douma chemical attack: Syria war in pictures A medical worker giving a toddler oxygen through respirators following an alleged poison gas attack in the opposition-held town of Douma. Syrian Civil Defense White Helmets via AP Douma chemical attack: Syria war in pictures An image grab taken from a video released by the Douma City Coordination Committee shows unidentified volunteers spraying a girl with water at a make-shift hospital following an alleged chemical attack AFP/Douma City Coordination Committee Douma chemical attack: Syria war in pictures A child is treated in a hospital in Douma White Helmets/Handout via Reuters Douma chemical attack: Syria war in pictures Injured victims of an alleged chemical attack in Douma EPA Douma chemical attack: Syria war in pictures An image grab taken from a video released by the Douma City Coordination Committee shows unidentified volunteers spraying a man with water at a make-shift hospital following an alleged chemical attack AFP/Douma City Coordination Committee Douma chemical attack: Syria war in pictures A Syrian man mourns after an alleged chemical attack Alamy Douma chemical attack: Syria war in pictures People stand in front of damaged buildings, in the town of Douma, the site of a suspected chemical weapons attack, near Damascus, Syria AP Photo/Hassan Ammar Douma chemical attack: Syria war in pictures Rubble lines a street in Douma, at the site of a suspected chemical weapons attack AP Douma chemical attack: Syria war in pictures Rubble fills a street in Douma, the site of a suspected chemical weapons attack, near Damascus AP

Chlorine, which the US assessed was used in the Douma attack, is a common industrial chemical that is not difficult to find or weaponise, experts say.

As a result, crippling a chlorine capability through military strikes is far more difficult than eliminating more sophisticated chemical or biological warfare agents.

Moved by the images of the civilian victims of the suspected chemical attack, Mr Trump made no secret he was convinced of the need for a powerful US response.

He even put Moscow and Tehran, which back the Assad regime, on edge with fiery rhetoric in the days before the strike, leaving open the possibility he might target them too.

But US officials familiar with US military planning told Reuters that Russia and Iran were never seriously considered as targets.

Beyond working to avoid civilian casualties, Mr Mattis and other US officials tailored the strikes in a way to avoid triggering retaliation from Moscow and Tehran.

The end result was an operation that did not target the Syrian regime’s conventional military infrastructure, including aircraft that could deliver chemical agents in the future.

The revelations came ahead of a meeting between the head of Russia’s military general staff and Nato’s supreme allied commander.

Valery Gerasimov and Curtis Scaparrotti are set to meet in Azerbaijan to discuss the situation in Syria, according to the Tass news agency, which cited the Russian defence ministry.

Syria bombings: US, UK and French military air strikes wreckage Show all 13 1 /13 Syria bombings: US, UK and French military air strikes wreckage Syria bombings: US, UK and French military air strikes wreckage The wreckage of the Scientific Studies and Research Centre in the Barzeh district, north of Damascus, which was targeted by the US, UK and France air strikes. AFP/Getty Syria bombings: US, UK and French military air strikes wreckage A Syrian soldier films the damage of the Syrian Scientific Research Center surrounded by papers and rubble. AP Syria bombings: US, UK and French military air strikes wreckage Firefighrers extinguish smoke that rises from the damage. The Pentagon says none of the missiles filed by the U.S. and its allies was deflected by Syrian air defenses, rebutting claims by the Russian and Syrian governments. AP Syria bombings: US, UK and French military air strikes wreckage The wreckage of part of the Scientific Studies and Research Centre compound . AFP/Getty Syria bombings: US, UK and French military air strikes wreckage Part of a building collapsing, surrounded by the wreckage. AFP/Getty Syria bombings: US, UK and French military air strikes wreckage Further damaged to the Scientific Studies and Research Centre compound. AFP/Getty Syria bombings: US, UK and French military air strikes wreckage Lt. Gen. Kenneth McKenzie, the director of the Joint Staff at the Pentagon, also says there also is no indication that Russian air defense systems were employed early Saturday in Syria. AP Syria bombings: US, UK and French military air strikes wreckage A Syrian soldier sprays water on the wreckage. AFP/Getty Syria bombings: US, UK and French military air strikes wreckage Syrian state news agency SANA reported several missiles hit a research centre in Barzeh, north of Damascus, "destroying a building that included scientific labs and a training centre". AFP/Getty Syria bombings: US, UK and French military air strikes wreckage A Syrian soldier films the damage. AP Syria bombings: US, UK and French military air strikes wreckage Damage to the Scientific Research Center building that was hit by the strikes. EPA Syria bombings: US, UK and French military air strikes wreckage The Scientific Studies and Research Centre was one of the targeted buildings by the US, UK and France. AFP/Getty Syria bombings: US, UK and French military air strikes wreckage Further damage to the centre. EPA

The talks are also expected to touch on Nato and Russian military activity in Europe, Tass added.

Meanwhile, Isis militants have been give 48 hours to agree to withdraw from their last bastion in the capital, Damascus.

Syrian troops and allied Palestinian fighters are massing around the Yarmouk refugee camp, which Isis seized in 2015 after months of heavy fighting.

The extremists have been driven from nearly all the territory they once controlled in Syria and Iraq.