Citing senior administration officials whose name it did not report, The New York Times said Thursday the president has not made a final decision on carrying out a limited military operation but a strike could come soon after U.N. inspectors leave Syria, possibly as early as Saturday.
The inspectors have been searching for evidence to determine who carried out a chemical weapons attack in which hundreds of Syrians were killed Aug. 21.
The administration officials said intelligence will show the attack was carried out by forces loyal to Syrian President Bashar Assad although it does not tie Assad directly to the attack, the Times reported.
The officials said the White House believes the information justifies a limited strike that it expects would deter the Syrian government from further use of chemical weapons.
They said Obama is predicating the case for a military response on U.S. national interest and standing up for international standards against chemical weapons.
Obama called House Speaker John Boehner, R-Ohio, Thursday to discuss prospects of a military strike against Syria, Boehner's office said.
Boehner Wednesday urged Obama to explain to Congress and the American people how a military strike on Syria "will secure U.S. objectives."
The Obama administration has been lining up support from other governments, including Britain, for a strike against Syria in retaliation for the chemical weapons attack.
Boehner told Obama in a letter Wednesday the U.S. response "to the deterioration and atrocities in Syria has implications not just in Syria, but also for America's credibility across the globe, especially in places like Iran."
"Even as the United States grapples with the alarming scale of the human suffering, we are immediately confronted with contemplating the potential scenarios our response might trigger or accelerate."
Boehner spokesman Brendan Buck said Thursday the speaker asked the president during Thursday's telephone call about the concerns he had brought up in the letter, "including the legal justification for any military strike, the policy and precedent such a response would set, and the objectives and strategy for any potential action," The Hill reported.
"Only the president can answer these questions, and it is clear that further dialogue and consultation with Congress, as well as communication with the American public, will be needed," Buck said.
White House spokesman Josh Earnest said Thursday the administration has consulted with Congress "in a robust way that has involved reading out some of the conversations that the president and others have had with our allies across the globe, that it has involved the sharing of some intelligence. ... It also includes a conversation about some of the options that are available to the president, in terms of a specific response to the Syrian regime's use of chemical weapons."
The White House said late Thursday senior administration officials held an unclassified conference call for key members of Congress "to brief them on the administration's thinking and seek their input on the U.S. response to the Assad regime's use of chemical weapons near Damascus on Aug. 21."
"The views of Congress are important to the president's decision-making process, and we will continue to engage with members as the president reaches a decision on the appropriate U.S. response to the Syrian government's violation of international norms against the use of chemical weapons," the White House statement said.
Secretary of State John Kerry, Defense Secretary Chuck Hagel, national security adviser Susan Rice, Director of National Intelligence James Clapper and Vice Chairman of the Joint Chiefs of Staff Sandy Winnefeld participated in the call, which lasted an hour and a half.
"I have previously called for the United States ... to increase the military pressure on the Assad regime by providing lethal aid to vetted elements of the Syrian opposition," Levin tweeted after the conference call.
Threats of retaliation by Syria's President Bashar Assad and Iran if Syria is attacked should not be taken lightly, Middle East analysts say.
Both Iran and Syria threatened to strike against Israel and other U.S. allies in the Middle East if there is a U.S. attack on Syria over its alleged use of chemical weapons against civilians.
Hundreds of Syrians in a rebel-held region near Damascus were reported killed in an Aug. 21 chemical attack.
"Iran is a huge threat," Ariel Cohen, a senior research fellow at the Heritage Foundation, told USA Today in an article published Wednesday.
Iran's ruling mullahs are Syria's main ally in the region and they consider survival of the Assad regime important, analysts said. Syria provides Iran a port on the Mediterranean Sea and a transit lane from Iran to Lebanon, where the Hezbollah terrorist organization and its cache of weapons are based.
If Iran decides to retaliate against U.S. allies to protect Assad, it could attack not only Israel but also other U.S. allies in the region, such as Saudi Arabia, the United Arab Emirates and Jordan.
Iran could try to block the Strait of Hormuz, which provides passage for about a fifth of the world's petroleum supply, Cohen told USA Today.
"When we keep an eye on Syria we need to keep an eye on the security of shipping, especially the shipping of oil in the straits," Cohen said.
U.S. forces in the region are prepared for such attacks but would not be able to prevent them all right away, said Chris Harmer, an Institute for the Study of War analyst and former naval commander.
Some analysts said Iran's current leadership is unlikely to retaliate.
Suzanne Maloney, an Iran expert at the Brookings Institution, and a former State Department policy planner under President George W. Bush, says public statements of Iran's new president, Hassan Rouhani, indicate he "wants to get out of this thing with limited damage to Iran's reputation."
"He clearly understands that if Iran gets into a shooting war with the United States, Europe and international intervention, it's likely to be a quicker path to regime elimination than any other," Maloney told USA Today.