Updated

Top congressional Democrats and Republicans differed Sunday about how the United States' effort to solve the Syria crisis swerved from a threat of military force to a possible diplomatic solution, but they agreed Russian President Vladimir Putin changed the course of action.

Rep. Chris Van Hollen, D-Md., argued that a potential diplomatic solution couldn’t have been possible without President Obama first saying the United States would take military action against Syrian President Bashar Assad for an Aug. 21 chemical weapons attack that killed nearly 1,500 of his own people.

“We wouldn’t be at this point if not for the president’s credible threat,” Van Hollen, the top Democrat on the House Budget Committee, told “Fox News Sunday.” “And at the end of the day, [Putin] helped deliver exactly what the United States wanted, which is to put an end to Assad's weapons of mass destruction.”

His argument appeared to be supported by New Jersey Democratic Sen. Robert Menendez, chairman of the Senate Foreign Relations Committee.

“This is a diplomatic breakthrough,” he told NBC’s “Meet the Press.” But “the only reason we've gotten to this point, even to this possibility” is because of the threat of American military action.

The shift happened in a swift turn of events starting Aug. 31 when Obama said the U.S. should launch a punitive strike, but that he also wanted congressional approval.

In the ensuing days, with Congress and the American public showing limited support for a strike, Secretary of State John Kerry seemed to float a plan for Syria to surrender its chemical weapons to the international community. Putin embraced the idea, and Kerry agreed Saturday with Russia to a tentative deal to secure Assad’s stockpile.

Van Hollen argued that Assad within that time went from denying having chemical weapons to admitting he has them to appearing open to allowing international inspectors into Syria, entrenched in a more than 2-year-long civil war.

Texas Republican Rep. Michael McCaul, chairman of the House Homeland Security Committee, suggested on Fox that the Obama administration sought a possible alternative to a military strike because there “was not a lot of appetite from the American people.”

Still, McCaul argued: “Russia has the greatest influence over Assad.”

Michigan Republican Rep. Mike Rogers, chairman of the House Intelligence Committee, said the U.S. is "being led by the nose by" Putin.

"So, if we wanted a transition with Assad, we just fired our last round, and we have taken our ability to negotiate a settlement from the White House, and we've sent it with Russia to the United Nations," he told CNN’s “State of the Union.” "That's a dangerous place for us to be.”

Syrian Minister of National Reconciliation Ali Haidar this weekend called the deal a "victory" for Assad's regime.

However, it remains unclear whether Assad will sign the agreement, which requires the Middle East country to submit a full inventory of its stocks within the next week and hand over all of the components of its program by mid-2014.

Still, the U.S. repeated Sunday that it could take military action should Assad fail to comply.

"The threat of force is real, and the Assad regime and all those taking part need to understand that President Obama and the United States are committed to achieve this goal," Kerry said in Jerusalem, where he briefed Israeli leaders on the agreement.

Another uncertainty is whether U.S. troops will be part of what is expected to be a Russian-led international effort to remove the chemical weapons, considering the Obama administration has repeatedly said there will be no American “boots on the ground.”

Obama said in an interview with ABC aired Sunday that he welcomes Putin's involvement, considering he is among Assad's closest allies.

"I think there's a way for Mr. Putin, despite me and him having a whole lot of differences, to play an important role," Obama said. "So I welcome him being involved. I welcome him saying, 'I will take responsibility for pushing my client, the Assad regime, to deal with these chemical weapons.' "

Obama also said he's taking a cautious approach to the allegiance but argued he has worked with Putin on other issues, despite their disagreements, pointing out that Putin has helped the United States transport supplies to its troops in Afghanistan.

Under the framework agreement, international inspectors are to be on the ground in Syria by November. During that month, they are to complete their initial assessment and all mixing and filling equipment for chemical weapons is to be destroyed.

Noncompliance by the Assad government or any other party would be referred to the 15-nation U.N. Security Council by the Organization for the Prohibition of Chemical Weapons. That group oversees the Chemical Weapons Convention, which Syria this week agreed to join.

The U.S. and Russia will press for a Security Council resolution enshrining the chemical weapons agreement under Chapter 7 of the U.N. Charter, which can authorize both the use of force and nonmilitary measures.

But Russia, which already has rejected three resolutions on Syria, would be sure to veto military action.

The Associated Press contributed to this report.