President Bashar Assad's forces have complied with the ceasefire in Syria "in the most grudging way possible" and could attempt to hinder the work of United Nations observers, William Hague has claimed.
The Foreign Secretary said he expected Assad's regime to attempt to use the ceasefire for its own advantage.
But he stressed that the situation, despite its imperfections, was a step forward from the intense bloodshed of recent months.
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Speaking in the Commons, Hague said it was right for MPs to have concerns about the regime's intentions.
He told Labour's Ian Murray: "You are quite right to raise doubts about the intentions of the regime, they have complied in the most grudging way possible with the ceasefire and not yet met all of its terms.
"They continued to kill as many people as they could in the opposition until the last possible moment.
"I have no doubt they will, at various stages, try to obstruct the observers and they do not necessarily intend to engage sincerely in any process of political transition.
"All of that is true, but it is an advance to have the observers there and the Security Council resolution in place."
Mr Murray asked for the Foreign Secretary's assessment of the cohesiveness of the opposition in Syria.
Mr Hague said: "I think the behaviour of the regime - not only in Homs now or in recent weeks, but throughout the last 13 months - can only help solidify and intensify the opposition.
"It is an encouragement to them because it shows what an appalling and murderous regime they are up against."
But Richard Ottaway, Tory chairman of the Foreign Affairs Select Committee, said the peace plan put forward by former UN secretary general Kofi Annan would reinforce the position of the Assad regime.
He said: "Ironically, compliance with the plan entrenches the regime in situ. Is it still your wish that the Assad regime stands down and how do you think this can be best achieved?"
Mr Hague said it was still the view of the Government that the Assad regime should go, but that was not the "united view" of the UN Security Council.
He said: "This resolution and the work of Kofi Annan is based on a process, a political process, but that is a process ... to lead to a plural, democratic, political system.
"Of course the regime will try to use a ceasefire and a political process to their own advantage.
"But the more it is a genuine ceasefire and the more it is a genuine political process, the less it will be to their advantage."
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