Syria's neighbours face a growing risk of the conflict spilling across their region as Bashar al-Assad turns to ever more desperate acts to halt rebels -- including the alleged use of chemical weapons.

Iraqi Prime Minister Nuri al-Maliki voiced such concerns on Saturday when he said a new wave of sectarian strife in his country stemmed from violence elsewhere, although he did not name Syria.

But analysts say Lebanon and Jordan will be the most vulnerable if the conflict spreads, while Iraq will also be affected along with Israel and Turkey.

"There is a significant risk of an increased spillover," said Anthony Skinner of British risk consultancy Maplecroft.

"It is a very vulnerable region and there is a risk of escalation. The whole region may increasingly become involved in the conflict."

Jordan hosts more than 500,000 Syrian refugees, while Lebanon is home to 400,000, but the two countries face other tough challenges.

Amman has found itself dragged closer to the conflict with the deployment of more US troops on its territory amid a warning by Assad the kingdom could be engulfed by the war, and accusations of allowing fighters into Syria.

"Jordan had been pushed because of the escalation next door and because of its concerns regarding militant Islam and Salafists. Jordan is concerned about the potential chaos that may follow for years or decades in the likely event that Assad will eventually be toppled," Skinner told AFP.

"Another key concept relates to the Jordanian Salafists who have crossed the borders into Syria in order to topple the regime."

Lebanon has witnessed frequent shelling from Syria of both Sunni Muslim and Shiite areas of its north and east.

It has adopted a policy of neutrality despite being torn between the Iran-backed Hezbollah and its allies that support Assad, and the Sunni-led March 14 movement that backs the revolt.

Opposition activists in Syria have accused Hezbollah of sending elite fighters to battle alongside Assad's troops in Qusayr, an area near the border.

"Lebanon could be plunging into a state of war -- this is a very real risk," Skinner said.

For Yezid Sayigh of the Carnegie Middle East Centre in Beirut, "the main impact on Jordan and Lebanon is the refugees, which puts them under severe pressure.

"Even those who support the Syrian opposition, are becoming fed up with the refugee influx. If the situation develops, more Syrians, maybe millions, will flee to Jordan and Lebanon," exacerbating the chances of conflict in the host countries, he told AFP.

Syria's conflict is increasingly becoming a proxy war, with the rebels backed by US allies Saudi Arabia, Qatar and Turkey, and Assad by Hezbollah, Iran and Russia.

Assad's forces are too stretched to retaliate against those who back the rebels, but occasional cross-border shelling is conceivable, said Skinner.

"Though, these attacks would not be deemed large enough to provoke a strong counter-punch, it's conceivable that Assad would use proxies that are not so clearly linked to his line of command."

Turkey and Israel are worried about the fallout.

"The threat of the Syrian conflict has pushed Turkey to engage in what appears to be a serious peace process with the PKK (Kurdistan Workers' Party)," said Skinner.

Israel fears Syria's chemical weapons arsenal could fall into the wrong hands.

"The United States and Israel have limited options to deal with the chemical weapons. They do not want things to develop, which might give the Syrian regime the chance to use the weapons," said Sayigh.

The opposition has urged the UN to act immediately, possibly even by imposing a no-fly zone, but US President Barack Obama is awaiting a "definitive" probe into their alleged use before taking any action.

Iraq was "obviously affected and there are sectarian tensions," said Sayigh. "Things might develop if the Iraqis failed to address their problems."

Emile Hokayem, analyst at the International Institute for Strategic Studies, said the conflict was "sucking" in neighbours, an effect at least partly due to Syrian "mischief".

"Syria has used a lot of mischief and pressure on its neighbours to punish them, keep them in check or conduct a form of blackmail to remind them of the regional cost of pushing the regime too far," he said.

"A spillover has already happened. The situation is only going to worsen... intensification of cross-border fighting, direct and indirect attacks, more refugees."