BEIRUT/WASHINGTON: U.S. President Barack Obama won the backing of two top Republicans in Congress in his call for limited U.S. strikes on Syria to punish President Bashar al-Assad for his suspected use of chemical weapons against civilians.
Speaking after the United Nations said 2 million Syrians had fled a conflict that posed the greatest threat to world peace since the Vietnam war, Obama said the United States also has a broader plan to help rebels defeat Assad's forces.
In remarks that appeared to question the legality of U.S. plans to strike Syria without U.N. backing, U.N. Secretary-General Ban Ki-moon said the use of force is only legal when it is in self-defence or with U.N. Security Council authorization.
He said that if U.N. inspectors confirm the use of chemical weapons in Syria, the Security Council, which has long been deadlocked on the 2-1/2-year Syrian civil war, should overcome its differences and take action.
Having startled friends and foes alike in the Middle East by delaying a punitive attack on Assad until Congress reconvenes and agrees, Obama met congressional leaders at the White House on Tuesday to urge a prompt decision and assure them it did not mean another long war like Iraq or Afghanistan.
John Boehner, the Republican speaker of the U.S. House of Representatives, and House Majority Leader Eric Cantor both pledged their support for military action after the meeting.
Votes are expected to be held in the U.S. Senate and House next week, with the Republican-led House presenting the tougher challenge for Obama.
The Republican House leadership has indicated the votes will be "conscience votes," meaning they will not seek to influence members' votes on party lines. All the same, it would have been a big blow to Obama if he had not secured the backing of the top two Republicans.
"I believe that my colleagues should support this call for action," Boehner told reporters.
The president said strikes aimed at punishing the use of chemical weapons would hurt Assad's forces while other U.S. action would bolster his opponents - though the White House has insisted it is not seeking "regime change."
"What we are envisioning is something limited. It is something proportional. It will degrade Assad's capabilities," Obama said. "At the same time we have a broader strategy that will allow us to upgrade the capabilities of the opposition."
Assad denies deploying poison gas that killed hundreds of civilians last month.
The Syrian opposition, which on Tuesday said a forensic scientist had defected to the rebel side bringing evidence of Assad forces' use of sarin gas in March, has appealed to Western allies to send them weapons and use their air power to end a war that has killed more than 100,000 and made millions homeless.
The presence in rebel ranks of Islamist militants, some of them close to al Qaeda, has made Western leaders wary, while at the same time the undoubted - and apparently accelerating - human cost of the conflict has brought pressure to intervene.
The chairman of the U.S. Senate Armed Services Committee said on Tuesday he was confident after talking with Obama that the United States would step up its support for "vetted" elements of the Syrian opposition.
Senator Carl Levin said he urged the president, a fellow Democrat, to arm the Syrian rebels a day after two influential Republican senators, John McCain and Lindsey Graham, sought similar assurances from Obama. Levin said he told the White House that the United States should provide rebels with arms such as anti-tank weapons "which cannot be turned on us."
Top House Democrat Nancy Pelosi also voiced support for military strikes after meeting Obama on Tuesday, but Obama will still have to persuade some lawmakers, including Democrats, who have said they are concerned the president's draft resolution could be too open-ended.
U.S. Secretary of State John Kerry and Secretary of Defense Chuck Hagel took the administration's message to a Senate Foreign Relations Committee hearing on Tuesday, where they were pressed on whether the resolution put to Congress would explicitly rule out the use of ground troops.
Kerry said the language of the resolution was still being worked out but it was important to leave options open for using troops in a scenario where " Syria imploded" and stockpiles of chemical weapons needed to be secured from extremists.
"I don't want to take off the table an option that might or might not be available to the president of the United States to secure our country," he said at the hearing.
But Kerry also said that "the president has no intention" of putting American troops on the ground to be involved in fighting Syria's civil war.
After two and a half years of war, nearly one Syrian in three has been driven from home by violence and fear.
The U.N. refugee agency UNHCR said there had been a near tenfold increase over the past 12 months in the rate of refugees crossing Syria's borders into Turkey, Iraq, Jordan and Lebanon - to a daily average of nearly 5,000 men, women and children.
This has pushed the total living abroad above 2 million.
That represents some 10 percent of Syria's population, the UNHCR said. With a further 4.25 million estimated to have been displaced but still resident inside the country, close to a third of all Syrians are living away from their original homes.
Comparing the figures to the peak of Afghanistan's refugee crisis two decades ago, U.N. High Commissioner for Refugees Antonio Guterres, said: " Syria has become the great tragedy of this century - a disgraceful humanitarian calamity with suffering and displacement unparalleled in recent history."
"The risks for global peace and security that the present Syria crisis represents, I'm sure, are not smaller than what we have witnessed in any other crisis that we have had since the Vietnam war," said Guterres, a former Portuguese prime minister.
Russia, backed by China, has used its veto power in the U.N. Security Council three times to block resolutions condemning Assad's government and threatening it with sanctions. Assad, like Russia, blames the rebels for the Aug. 21 gas attack.
Obama has said he is "comfortable going forward without the approval of a United Nations Security Council that so far has been completely paralysed and unwilling to hold Assad accountable."
Ban questioned whether the use of force to deter Syria or other countries from deploying chemical arms in the future could do more harm than good.
"We must consider the impact of any punitive measure on efforts to prevent further bloodshed and facilitate a political resolution of the conflict," he said, calling for renewed diplomatic efforts to solve the crisis.
The conflict has divided the Middle East on sectarian lines, with Shi'ite Iran backing Assad and Washington's Sunni Arab Gulf allies supporting the mainly Sunni rebels. It has also revived Cold War-style tensions between the Western powers and Moscow.
In an interview in Tuesday's Le Figaro, Assad told the Paris newspaper: "Everybody will lose control of the situation when the powder keg blows. There is a risk of a regional war."