The world is waiting to see whether the United States will strike against the Syrian regime -- and whether anyone will join in.
U.S. President Barack Obama said there's no doubt Syria used chemical weapons on its own civilians and he wants to launch attacks, but he first wants to get Congress' approval after lawmakers come back from recess September 9.
Meanwhile, a flurry of other developments has emerged. Here are the latest developments for Monday:
-- Secretary of State John Kerry, Defense Secretary Chuck Hagel and Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, are scheduled to appear before the Senate Foreign Relations Committee on Tuesday. A senior State Department official said Kerry will argue that failure to act "unravels the deterrent impact of the international norm against chemical weapons use."
-- U.S. Sens. John McCain and Lindsey Graham, both Republicans, met Monday with President Barack Obama on Syria. Afterward, McCain told reporters that he is more supportive of a limited military strike on Syria than he had been before the meeting, partly because the administration signaled increased support for the Syrian opposition.
-- McCain is a longtime advocate of U.S. intervention in Syria, and he criticized the Obama administration for delaying action to seek the approval of Congress. But he said failure to authorize military action would be "catastrophic."
-- Kerry told House Democrats in a phone call Monday that Turkey, Saudi Arabia and the United Arab Emirates have offered military assets for any action planned for Syria, two sources on the call told CNN's Dana Bash.
-- Rep. Janice Hahn, D-California, told CNN's "Around the World" that she remains concerned about the duration and scope of any military action and that the administration still faces many questions from Congress. Hahn said she has been briefed by administration officials twice in the past two days.
-- The Obama administration will conduct classified briefings regarding Syria for Congress almost every day this week, CNN's Dana Bash has learned.
Kerry also said more countries will move toward supporting such action. The sources said 127 Democratic lawmakers were on the 70-minute call with Kerry, National Security Adviser Susan Rice, Defense Secretary Chuck Hagel and Chairman of the Joint Chiefs of Staff Martin Dempsey.
-- Kerry will testify before congressional committees Wednesday, congressional sources said. He will testify to the House Foreign Affairs Committee, while he will join Director of National Intelligence James Clapper in a classified briefing for the Senate Foreign Relations Committee on Wednesday morning.
-- Sens. Harry Reid and Robert Menendez, two top Democrats, are working to narrow the scope of President Obama's proposed authorization to use force in Syria, a Democratic leadership source said Monday. There have been concerns that the original draft doesn't have an expiration date and doesn't explicitly prohibit forces on the ground.
-- Even if Obama gets Congress' approval to strike Syrian targets, he might still violate international law. Under the 1973 War Powers Resolution, a president can initiate an attack as long as he notifies Congress within 48 hours. But that's a U.S. law. The United Nations' charter generally doesn't allow countries to attack other nations unless in self-defense or with approval from the U.N. Security Council -- neither of which is the case in Syria.
-- Congressional approval wouldn't solve the problem with international law, a senior administration official said, but it would enhance the legitimacy of military action.
-- Several U.S. Navy ships, led by the aircraft carrier USS Nimitz, are now in the Red Sea, a U.S. official said Monday. A second official said the Nimitz is not expected to participate in combat operations over Syria, but the ship is there for a greater U.S. military presence in the region.
-- NATO Secretary General Anders Fogh Rasmussen said he thinks a "strong response to the use of chemical weapons is needed." But, he told reporters in Brussels on Monday, he doesn't "see a long-term sustainable military solution" to the Syrian conflict and stressed the need for a "political process."
-- Rasmussen said he's "convinced that the Syrian regime is responsible" for a chemical attack last month. He said "many facts" point to that conclusion.
-- Asked about alleged chemical weapons use in Syria, Rasmussen said there needs to be a firm international reaction to avoid future chemical attacks. "It would send a very dangerous signal to dictators all over the world if we stand ... by and don't react," he said. "The question is how to react and when to react."
-- NATO is playing its part in the crisis in Syria through the deployment of Patriot missiles in Turkey for protection of that country's population, Rasmussen told reporters Monday. But if Turkey, a NATO member, is attacked, allies would have to gather and discuss how to respond. "We are prepared to defend Turkey effectively," he said.
-- The Middle East "is a powder keg" that will explode if Syria is attacked, Syrian President Bashar al-Assad told French newspaper Le Figaro in an interview published in part Monday.
-- The pro-regime Syrian Electronic Army appears to have hacked the U.S. Marines recruitment website, marines.com, and posted a letter urging Marines not to attack Syria.