WASHINGTON — President Obama said Friday he would respond ‘‘prudently’’ and ‘‘deliberately’’ to evidence that Syria has used chemical weapons, tamping down any expectations he would take swift action after a US intelligence assessment that the Syrian government has likely used the chemical agent sarin on a small scale in the nation’s civil war.
Obama’s remarks, before a meeting here with King Abdullah of Jordan, laid bare the quandary he now faces: The day after the White House, in a letter to congressional leaders, said the nation’s intelligence agencies assessed ‘‘with varying degrees of confidence’’ that the Syrian government had used sarin, the president said he was seeking further proof of culpability for chemical-weapons attacks — a laborious process that analysts say may never produce a definitive judgment. But Obama is also trying to preserve his credibility after previously warning that the use of chemical weapons would be a ‘‘game changer’’ and prompt a forceful American response.
‘‘Knowing that potentially chemical weapons have been used inside of Syria doesn’t tell us when they were used, how they were used,’’ Obama told reporters in the Oval Office. ‘‘We have to act prudently. We have to make these assessments deliberately.
‘‘But I meant what I’d said,’’ the president added. ‘‘To use potential weapons of mass destruction on civilian populations crosses another line with respect to international norms and international law. And that is going to be a game changer.’’
At the same time, the White House cited the Iraq War to justify its wariness of taking action against another Arab country on the basis of incomplete or potentially inaccurate assessments of its weapons of mass destruction. The press secretary, Jay Carney, said the White House would ‘‘look at the past for guidance when it comes to the need to be very serious about gathering all the facts, establishing chain of custody, linking evidence of the use of chemical weapons to specific incidents and actions taken by the regime.’’
As Obama and his aides walked a fine line on how to confront the evidence about chemical weapons, they engaged in an intensified round of diplomacy with Arab leaders to bolster support for the Syrian opposition and to try to develop a consensus on how to deal with the escalating strife.
In addition to King Abdullah, Obama met in recent days with leaders from Qatar and the United Arab Emirates, as well as the Saudi foreign minister. Next month, he will meet Prime Minister Recep Tayyip Erdogan of Turkey, which borders Syria and is among the countries most exposed to the threat of chemical weapons.
‘‘If their policy is premised on not going it alone, even in response to chemical weapons,’’ said Brian Katulis, a Middle East expert at the Center for American Progress, ‘‘you’re going to need a lot of people reading from the same songsheet.’’
The more pressing problem, Katulis said, was that the president’s strong warnings to Syria ‘‘are running ahead of their policy.’’
A major focus of the meeting with King Abdullah, a senior administration official said, was coordinating more robust aid for the Syrian opposition. The United States has pledged to double its nonlethal assistance, and the official said it was working with regional allies to direct it to reliable opposition groups.
On Friday, Prime Minister David Cameron of Britain echoed Obama’s cautious assessment of the use of chemical weapons, saying there was limited but growing evidence that such weapons had been used, probably by government forces.
The British government, like the White House, is concerned about avoiding a repetition of events that led to the 2003 invasion of Iraq when the presence of unconventional weapons, cited as justification for military action, had not been corroborated.
The United States has called on the United Nations to carry out a thorough investigation of the suspected use of chemical weapons. But the government of Bashar Assad has not allowed inspectors into the country and, backed by its supporter Russia, is insisting on limiting the scope of the investigation.
“As long as Damascus refuses to let the UN investigate all allegations, and as long as Russia provides the regime with political cover at the Security Council, it may be impossible for Washington to meet that standard,’’ Michael Eisenstadt, director of the military and security studies program at the Washington Institute for Near East Policy, said in a report.
‘Knowing that potentially chemical weapons have been used ... doesn’t tell us when they were used, how they were used. We have to act prudently.’President Obama
The risk of not responding now, even with less than definitive proof, Eisenstadt said, is that it could embolden Assad to use chemical weapons on a wider scale.