Experts from the world's global chemical arms watchdog are continuing their mission to probe an alleged gas attack in Douma despite Western air strikes in Syria, the body said Saturday.
"There is no practicable alternative to the use of force to degrade and deter the use of chemical weapons by the Syrian regime", May said in a televised statement. "We are prepared to sustain this response until the Syrian regime stops its use of prohibited chemical agents", he said.
The U.S. military targeted a research center, a storage facility that is believed to have a stockpile of chemical weapons and a command post in Syria, the Pentagon said late Friday night.
"It was right to take the action that we have done in the timing that we have done", she said.
The US president claimed that the joint action was meant to establish a "strong deterrent" against the production, spread, and use of chemical weapons.
She said she authorized British forces to join in the strikes after intelligence indicated Syrian president Bashar al-Assad's government was responsible for an attack using chemical weapons in the Damascus suburb of Douma a week ago.
"I have done so because I judge this action to be in Britain's national interest".More news: Questions Facebook CEO Mark Zuckerberg didn't answer in U.S. hearing
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Britain has blamed Russian Federation for the poisoning - a charge vehemently denied by Moscow which has accused London of failing to come up with evidence for its claims.
"Our service personnel have played an important role in terms of degrading the ability of the Syrian regime to use chemical weapons in the future", Williamson said.
May is not obliged to win parliament's approval before ordering military action, but a non-binding constitutional convention to do so has been established since a 2003 vote on joining the USA -led invasion of Iraq.
May held an emergency cabinet meeting to discuss possible action on Thursday and there had been calls for the British parliament to be consulted before any air strikes.
Meanwhile Labour leader Jeremy Corbyn has said Parliament should have been given a vote ahead of the strikes.
She said that at an emergency cabinet meeting in London on Thursday "we agreed that it was both right and legal to take military action" after hearing legal advice. "It is not about regime change", May said in statement made from her country residence at Chequers just minutes after U.S. President Donald Trump announced the strikes from the White House.