Downing Street has warned the regime of President Bashar Assad that "we will not abandon" the people of Syria following the Houla massacre.
David Cameron convened a meeting of the National Security Council which considered "all the options on the table" for dealing with the Assad regime.
"The Prime Minister wants to be sure that we are doing all we can to bring an end to the violence in Syria and to support the process of transition," a Number 10 spokesman said.
Cameron: "We will not abandon Syrian people"
The council agreed that further sanctions against Syria should be considered if the regime does not comply with the peace plan brokered by former UN secretary-general Kofi Annan.
The spokesman said: "The Prime Minister convened a meeting of the National Security Council today to discuss the situation in Syria following the sickening massacre at Houla and the escalation in violence in recent days.
"The Prime Minister wants to be sure that we are doing all we can to bring an end to the violence in Syria and to support the process of transition.
"The National Security Council considered the range of diplomatic efforts being pursued by the Government and agreed that we need to keep working with our international partners to make clear to the Assad regime that they must comply with the Annan plan, to stop killing and maiming their own citizens and that those responsible for the brutal violence will be held accountable for their actions.
"They agreed that we should step up these efforts, including considering further sanctions. It is in the interest of everyone to put in place an orderly democratic transition that meets the aspirations of the Syrian people.
"The National Security Council considered all the options on the table.
"Our goal is a peaceful political transition and our focus remains on the Annan plan but the Assad regime should not make the mistake of believing that we will abandon the Syrian people.
"Today's meeting of the National Security Council comes after increased efforts by the Government to find a solution to the crisis."
The meeting follows a round of international talks involving senior members of the Government.
On Monday, the Prime Minister spoke to French President Francois Hollande and UN Secretary-General Ban Ki-moon.
Foreign Secretary William Hague visited Moscow for talks with his Russian counterpart and will hold further discussions at a summit in Turkey.
Earlier this week the Government expelled three Syrian diplomats from the UK.
The spokesman said the UN Human Rights Council will hold an emergency session in Geneva on Friday, at the request of the UK, to discuss the situation in Syria.
"We will keep up these efforts in the weeks ahead to help increase the international pressure on the regime to bring this oppression to an end," he added.
Hague said he would like to see President Assad appear at the International Criminal Court (ICC) over the Houla massacre but there was little hope of the UN Security Council agreeing to refer the regime to the tribunal.
Hague: "Assad should appear before the International Criminal Court"
Russia and China, both permanent members of the council with the power of veto, have been reluctant to support the action demanded by the UK and others at the international institution.
Asked on Channel 4 News if the Syrian leader should be in the dock at the ICC, Hague said: "Yes, that would be my personal view. Of course terrible crimes have been committed, there must be no impunity for those crimes."
"Britain has sent teams to the borders of Syria to assemble evidence. We've done that over recent months about earlier crimes that have been committed and we have helped bring together in the international community the ability to collect the evidence about such crimes.
"But this subject takes us back to the problem at the UN Security Council where we have united behind the Annan plan but not behind stronger action.
"To refer Syria, a country which is not a party to the International Criminal Court, to that court would require a resolution of the UN Security Council and there we, of course, are blocked."
He told Channel 4 News urgent action was needed to prevent a descent into all-out civil war.
"One of the great dangers here is that Syria could collapse into a sectarian civil war in which casualties could be far greater even than the horrific scenes and the terrible toll that we have seen already.
"So there is a real urgency to this. It is hard to tell from the outside when such a collapse would take place."
Hague said he would meet Syrian opposition groups in Istanbul on Friday to discuss the situation.
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