UN Secretary-General Ban Ki-moon on Friday called for greater efforts to help bring an end to the conflict in Syria, where the crisis and violence have been going on for 20 months, as well as greater support for the international envoy tasked with that mission.

"We can only succeed if all sides take the necessary steps, and if there are converging actions by the international community, in particular the Security Council," the secretary-general made the statement he was speaking at an informal meeting of the UN General Assembly at UN Headquarters in New York.

Ban also announced his plans to visit displaced Syrians in refugee camps in Turkey and Jordan, which, together with Lebanon and Iraq, are the major countries in the region to receive a large influx of Syrian refugees.

"If we genuinely unite behind Mr. Brahimi and behind one process, it is still possible to avert the worst and enable a Syria in peace to emerge from this crisis," he added, referring to the joint special representative of the UN and the Arab League for Syria, Lakhdar Brahimi, who also briefed the Assembly on Friday.

The crisis and conflict in Syria, which broke out in March 2011, has led to the deaths of at least 20,000 people, mostly civilians, forced more than 460,000 people to flee to neighboring countries, and left more than 2.5 million people in need of humanitarian assistance, according to UN estimates.

The Security Council, which Brahimi briefed on Thursday, has met several times on the situation in Syria, but has so far not reached agreement on collective action to tackle the conflict.

In his remarks, Ban highlighted the humanitarian aspects of the crisis, describing it as "becoming more acute," with potentially up to four million people inside of Syria in need of aid before the New Year due to the onset of winter.

"The flow of refugees also continues, with ever more serious impact on regional security -- we expect the total number of refugees to reach 700,000 by early next year," he said.

"At the same time, the Syria Humanitarian Assistance Response Plan is only 50 percent funded and the Regional Response Plan is only 38 percent funded," he said. "We continue to ask urgently for additional funds and improved access to all those needing humanitarian assistance."

The Syrian Humanitarian Assistance Response Plan seeks 348 million U.S. dollars but has so far received 157 million dollars, while the revised Regional Response Plan, launched in September, seeks 487.9 million dollars. The former seeks to cover humanitarian relief activities inside Syria, while the latter represents the combined planning of 52 UN agencies and non- governmental organizations to support Syrian refugees in neighboring countries.

Meanwhile, the secretary-general said he planned to soon visit refugee camps in Jordan and Turkey to assess the situation on the ground, and reiterated his view that "building a free and democratic Syria will require political dialogue and negotiations, " and that the United Nations would help facilitate such a process.

In his speech to the General Assembly, Brahimi highlighted the worsening security situation on the ground, where the "fighting has expanded geographically to almost all parts of Syria and intensified very significantly."

Brahimi, the former Algerian foreign minister and the UN trouble shooter, pointed to recent incidents involving peacekeepers from the UN Disengagement Observer Force (UNDOF) as examples of the further deterioration of the security situation.

On Thursday, an UNDOF convoy was carrying troops scheduled to rotate out of the Golan Heights, where they monitor the 1974 disengagement accord between Syria and Israel after their 1973 war, when it came under gun fire in an area of Damascus where military operations between the Syrian armed forces and armed members of the opposition were taking place. UNDOF peacekeepers came under fire on Friday, as well, UN officials said here.

In addition, over the past fortnight there have been reported clashes in the Golan Heights between Syrian security forces and the opposition.

"In other words, threats to regional peace and stability are neither abstract nor something in the distant future," Brahimi said. "Countries in the region are already bearing the burden of hundreds of thousands of refugees and, in many instances, tensions are real and mounting within parts of their respective societies between supporters and opponents of the Syrian regime."

He said that in his opinion, there were only two options for the way forward in Syria.

"Either a political process that leads to the creation of a new Syria, with a new political dispensation that puts an end to the present tragedy, satisfies the legitimate aspirations of the Syrian people to dignity, freedom, democracy, social justice and equality between all its citizens and preserves the sovereignty and unity of the country," he said. "Or, Syria becomes a failed state with all the predictable, dire consequences for the people of Syria, for the entire region and for international peace and security."

With nobody wanting to see Syria become a failed state, he added, the "only option everyone should opt for and work for is a negotiated political process."

Brahimi, who was appointed to replace Kofi Annan, the former UN secretary-general, in September after his failure to bring an end to the Syrian crisis, said that the parties on the ground would have to buy into any such process, and given the breakdown in relations with many neighbouring countries, he did not think it was possible for them to put together a workable peace plan in the foreseeable future.

"We are left, therefore, with this Organization, the United Nations, and, in particular, its Security Council," he said. " Difficult as it has been for the Council to reach a consensus on an implementable roadmap for Syria -- I nevertheless feel that it is here, and only here, that a credible, implementable process can be put together."

He noted that many of the building blocks for a political process to end the crisis in Syria are already contained in the communique of the Action Group for Syria, announced in Geneva in late June.

Amongst other items, the document called for the establishment of a transitional governing body, with full executive powers and made up by members of the present government and the opposition and other groups, as part of important agreed principles and guidelines for a Syrian-led political transition.

"For the Geneva document to be effective, its substantive parts -- together with additional elements, as necessary need to be translated into a Security Council resolution. I know that a first attempt has failed," Brahimi said. "But that a first attempt to craft such a resolution failed does not mean it will be impossible for other attempts to succeed."

The Action Group is made up of the UN secretaries-general and the Arab League, the foreign ministers of the five permanent members of the Security Council -- China, France, Russia, the United Kingdom and the United States -- as well as the Turkish foreign minister, the high representative of the European Union for foreign affairs and security policy, and the foreign ministers of Iraq, Kuwait and Qatar, in their respective roles related to the Arab League.

The joint special representative also noted that any peace process must include a binding agreement on the cessation of all forms of violence, and for the fighting to stop a well-planned observation system must be put in place and "such observation can best be organized through a large, robust peacekeeping force and, naturally, that cannot be envisaged with a Security Council resolution."

The Security Council is responsible for determining the deployment of UN peacekeeping operation and formally authorizes such actions through the adoption of resolutions which set out the operation's mandate and size, and details the tasks it will be responsible for performing.