By Elizabeth Piper
LONDON (Reuters) - There are no plans as yet to repeat missile strikes on Syria, but Britain will consider further action if President Bashar al-Assad again uses chemical weapons against his people, foreign minister Boris Johnson said on Sunday.
In a show of support for Prime Minister Theresa May's decision to join the United States and France in attacking chemical weapons facilities in Syria on Saturday, her one-time political rival Johnson said it was the right thing to do.
But the prime minister may not find such backing when she faces parliament on Monday, where some lawmakers are angry that May took military action without their approval - a process that has increasingly become a tradition in Britain.
Speaking to the BBC, Johnson said what he described as the successful strikes on three sites in Syria were a message from the world that enough was enough, but acknowledged he could not say whether Assad still had chemical weapons.
"There is no proposal on the table at the moment for further attacks because so far, thank heavens, the Assad regime have not been so foolish as to launch another chemical weapons attack," he told the Andrew Marr show.
"If and when such a thing were to happen then clearly, with allies, we would study what the options were."
May, whose leadership has been questioned after scandals, divisions over Brexit and an ill-judged election that lost her party its majority in parliament, has found support from other international leaders for backing action against Syria.
But her move to add British Tornado jets to U.S. and French forces that launched around 105 missiles in the early hours of Saturday might be met with retaliatory measures by Syrian ally Russia and breaks with a convention to obtain parliamentary approval for military action dating back to the 2003 Iraq war.
The missile attacks were launched in retaliation for a suspected poison gas attack a week ago, a response Syria and its allies Russia and Iran have said violates international law. Moscow has denied any gas attack happened in Douma, instead accusing Britain of staging it to whip up anti-Russian hysteria.
QUESTION OF TIMING
Johnson said May and her cabinet of top ministers had to move quickly on Syria, so could not risk recalling parliament from its holiday break, and added that there were plenty of examples of when a prime minister did not get its approval.
May will make a statement on the action to the House of Commons on Monday, but opposition lawmakers have lined up to call for a more meaningful debate and a possible retrospective vote on the action, which would severely test her position.
Asked whether he would back a vote at the end of Monday's debate, opposition Labour leader Jeremy Corbyn told the BBC: "Yes I would, because I think parliament should have a say in this and the prime minister could quite easily have done that."
Corbyn, who questions the legal basis for the decision to join the strikes and accuses May of just following U.S. President Donald Trump, said the vote could set out future strategy for Syria, where a seven-year war has killed more than half a million people.
Scottish First Minister Nicola Sturgeon said sidelining parliament was "a serious mistake", while leader of the Green Party Caroline Lucas accused May of timing the strikes to "avoid a debate in parliament", which she described as "outrageous".
Washington, Paris and London have all described the strikes as a success, but Johnson acknowledged he did not know whether Assad could still possess chemical weapons and activity in Syria would be monitored on a daily basis.
All will be mindful of how military action can backfire. Former Prime Minister Tony Blair's legacy was tainted by his decision to join the war against Iraq, especially after an inquiry concluded that the decision to press ahead was based on flawed intelligence.
Opinion polls suggest that most Britons, still scarred by the Iraq conflict, do not support military action, with one by Survation taken after the strikes were launched saying 40 percent of the 2,060 people asked opposed the action. Some 36 percent supported the strikes.
Britain is also wary of any retaliatory action by Moscow, which May blamed for the nerve agent poisoning of former Russian spy Sergei Skripal and his daughter Yulia last month.
Johnson said Britain would take every possible precaution to defend against any Russian cyber attacks but that London would keep talking to Moscow as it did not "relish" their difficult relationship.
"This has been a successful mission," Johnson told CNN television. "I hope that this will be a deterrent to him and obviously I hope that it will mean no further humanitarian suffering by the Syrian people as a result of the use of chemical weapons."
(Reporting by Elizabeth Piper; Editing by Adrian Croft)