"The consequences are too great for Congress to be pushed aside."
Rep. Peter King, a New York Republican and influential member of the House Homeland Security Committee, said the U.S. response to the Syria situation will influence another regional proliferation issue -- Iran's potential development of nuclear weapons.
Obama "time and again has basically said that Iran will not be allowed to have nuclear weapons, that's the red line," King told CNN on Monday, adding that failure to enforce a similar threat against Syria on chemical weapons would undermine the president.
"This is as much a warning to Iran as I see it, as it is action against Syria," King said.
Even some in Obama's own party are cautioning against action that's not suitably inclusive. Sen. Jack Reed of Rhode Island told CNN on Monday the United States should only act in concert with an international coalition from at least NATO allies and Arab League members.
"Without their participation, it looks as if this is just a Western-vs.-Islamic struggle. It's not," said Reed, a member of the Senate Armed Services Committee. "This is to vindicate a basic rule of international law that these weapons will not be used, not by Iran, not by any power."
Reed said the most realistic option would be cruise missiles launched from U.S. Navy ships at sea, noting that "we can have precision weapons that could be fired and keep our aircraft out of Syrian airspace and away from their anti-aircraft systems."
"The most effective targets would have command-and-control, because you could send a signal to the Syrian regime that if they don't agree to international standards, if they don't make it clear and make it obvious that they're not going to use these weapons, and that we can inflict additional damage on their command-and-control," he added.
Earlier, a senior administration official said that assuming Obama decides to go ahead with a military response, any action could come as early as mid-week.
Factors weighing into the timing of any action include a desire to get it done before the president leaves for Russia next week for a summit with G8 allies, and before the administration has to make a decision on whether to suspend aid to Egypt because of the ongoing political turmoil there, the official explained.
American officials are consulting with allies to ensure they are supportive of any U.S. action, which the senior administration official said would be very limited in scope and a direct reaction to the use of chemical weapons. Representatives of three allied governments involved in those top-level consultations said the goal is to reach a consensus as soon as possible.
"No one is talking about a long process," one European diplomat told CNN.
Russia, China opposition make U.N. action unlikely
While U.N. Secretary-General Ban Ki-moon said Monday that the use of chemical weapons was a crime against humanity and must be punished, certain opposition by Syrian ally Russia and possibly China undermined the possibility that the Security Council would support a military mission.
Instead, a limited coalition of NATO partners such as Germany, France and Britain -- all of which have called for action against Syria -- and some Arab League members appeared more likely to provide political backing for Obama to order U.S. missile strikes.
Marie Harf, a State Department spokeswoman, said Kerry spoke Monday with his British, Jordanian, Qatari and Saudi counterparts, as well as the secretary-general of the Arab League.
The diplomatic efforts appeared to be working, with an Arab League spokesman condemning the al-Assad regime Tuesday for the chemical attack.
In another move, the United States postponed its involvement in talks scheduled for this week in Geneva on seeking a political solution to the Syrian civil war. Russia expressed disappointment at the U.S. decision and warned against any Western military strike on Syria.
Last month, Joint Chiefs Chairman Gen. Martin Dempsey provided Congress with a list of declassified U.S. military options for Syria that emphasized the high costs and risks of what he said would amount to "an act of war" at a time of deep budget cuts.
Dempsey's letter, dated July 19, listed U.S. assets in the region including Patriot missile defense batteries in Turkey and Jordan, as well as F-16 jet fighters positioned to defend Jordan from possible cross-border trouble. In addition, the Pentagon has sent four warships armed with cruise missiles to the region.
According to U.S. officials, updated options offered to the president in recent days included:
• Cruise missiles fired from one of four Navy destroyers deployed in the Mediterranean Sea. The missiles would be used to strike "command and control" facilities such as command bunkers, or the Syrian regime's means of delivering chemical weapons: artillery batteries and launchers. There is no indication that the missiles would strike actual chemical weapons stockpiles.
• Military jets firings weapons from outside Syrian airspace. This option carries additional risks and is considered less likely.
To Aaron David Miller, a vice president at the Woodrow Wilson International Center, the situation is forcing Obama to shift from being an "avoider-in-chief" regarding military involvement in Syria.
"It's almost inevitable that the president will authorize some form of military action," Miller told National Public Radio in an interview broadcast Monday.