Correction: A previous version of this article incorrectly said President Obama was scheduled to have bilateral talks with British Prime Minister David Cameron at the G-20 summit. Obama will meet with Chinese President Xi Jinping, along with French President François Hollande and Japanese Prime Minister Shinzo Abe. This version has been corrected.

President Obama took his campaign for a punitive military strike against Syria overseas on Wednesday, declaring that “the international community cannot be silent” and that its credibility is on the line as his request for congressional approval of such action moved ahead in the Senate.

But Obama faced fresh resistance from Russia, Syria’s stalwart patron, as President Vladi­mir Putin asserted that the West’s case against Syrian President Bashar al-Assad with respect to his regime’s alleged chemical weapons attack on civilians is “absurd” and does not stand up to scrutiny.

In Washington on Wednesday, the Senate Foreign Relations Committee backed military action after two days of hearings, but not before changing the text of the resolution to stress the goal of strengthening Syrian rebels and weakening Assad.

The full Senate could vote as soon as next week on an authorization that expressly prohibits putting any U.S. troops in Syria and gives the president a 90-day window to complete military action. The House is considering a similar resolution.

Obama will make a major push for global support for a U.S.-led strike against Syria once he arrives in St. Petersburg on Thursday for the Group of 20 economic summit hosted by Putin. The challenge he faces came into stark relief here Wednesday, however, when Swedish Prime Minister Fredrik Reinfeldt said after meeting with Obama that his small nation could not support a unilateral response.

“At what point do we say we need to confront actions that are violating our common humanity?” Obama said at a news conference in Stockholm. “I would argue that when I see 400 children subjected to gas, over 1,400 innocent civilians dying senselessly . . . the moral thing to do is not to stand by and do nothing.”

Obama said responsibility falls on Congress and the world to respond to the Syrian regime’s “horrific” use of chemical weapons.

“I didn’t set a red line,” he told reporters. “The world set a red line when governments representing 98 percent of the world’s population said the use of chemical weapons is abhorrent and passed a treaty forbidding their use, even when countries are engaged in war. Congress set a red line when it ratified that treaty.”

Obama and his administration have said Assad is directly responsible for the alleged sarin gas attack on civilians in the suburbs of Damascus on Aug. 21. But Putin said Syria poses no threat to the United States. He also said he is skeptical of U.S. intelligence, going so far as to accuse Secretary of State John F. Kerry of lying in his testimony to Congress this week.

“It ought to be convincing,” the Russian leader told the Associated Press in an interview published Wednesday. “It shouldn’t be based on some rumors and information obtained by the special services through some kind of eavesdropping, some conversations and things like that.”

Putin also said he finds it unlikely that Assad would risk international repercussions by using long-banned chemical weapons to kill men, women and children.

At a meeting of the presidential human rights council in Moscow on Wednesday, he accused the U.S. Senate of “legitimizing aggression,” adding: “We have all glued ourselves to TV screens and are waiting to see whether there will be a sanction or not. What we should be talking about is that this is absurd in principle.”

Russia has blocked proposals for U.N. Security Council action against Syria. In the AP interview, Putin warned the United States against launching a unilateral strike and said Russia is developing a plan of action in case it does so without U.N. approval, although he declined to cite specifics.

Yet he also said that if the United States and its allies could provide sufficient evidence that Assad’s forces carried out the Aug. 21 attack, Russia would consider allowing U.N. action against Syria. He added that Russia has frozen the shipment of certain parts for S-300 antiaircraft missiles that it had agreed to sell to Assad’s regime.

In his visit to Stockholm — a trip the White House hastily arranged after Obama called off a Moscow meeting with Putin planned for this week — Obama addressed the strained U.S.-Russian relations, acknowledging that he and Putin have “hit a wall.” He said Russia has not acknowledged “some of the terrible behavior of the Assad regime” and is preventing the kind of political transition in Syria that could stabilize the war-torn country.

Obama made an indirect reference to Russia’s controversial new law criminalizing “homosexual propaganda,” which has drawn attention ahead of the G-20 summit. “Our gay and lesbian brothers and sisters must be treated equally under the law,” he said, adding, “Our societies are strengthened and not weakened by diversity.”

At the G-20 summit, Obama has no meeting planned with Putin, but he has scheduled bilateral talks with Chinese President Xi Jinping, French President François Hollande and Japanese Prime Minister Shinzo Abe. U.S. officials said he plans to press his case on Syria in those sessions.

The resolution approved by the Senate panel Wednesday requires that the White House plan for a way to end the war in Syria through diplomatic means but suggests that the administration’s goal of a negotiated settlement is untenable. Military action should focus on “decisive changes to the present military balance of power” in Syria’s civil war, the key panel said.

Sen. John McCain (R-Ariz.), a key hawk who introduced the language, said in a statement that the changes “put the Congress on the record that this is the policy of the United States, as President Obama has assured me it is.”

The panel voted 10 to 7, with seven Democrats joined by three Republicans in favor, while two Democrats joined five Republicans in voting no. Edward J. Markey (D-Mass.), the Senate’s newest member, voted “present.”

White House press secretary Jay Carney welcomed the vote and praised senators for coming together across party lines.

McCain and Sens. Bob Corker (Tenn.) and Jeff Flake (Ariz.) were the three Republicans who voted with the Democratic majority.

But the vote exposed deep divisions in both parties and demonstrated how the possibility of military engagement in Syria has scrambled political allegiances — unlike other issues in recent years. Two of the committee’s most liberal members — Sens. Tom Udall (N.M.) and Chris Murphy (Conn.) — joined five conservatives in opposition, including Sens. Marco Rubio (Fla.) and Rand Paul (Ky.), who are considered leading possible GOP presidential contenders in 2016.

During a separate hearing in the House, Kerry said some Arab states are among more than 30 nations supporting U.S. military strikes, even though the Arab League declined to back that option last month. A few Arab states even offered to pay for the military operation, he said.

Offers have been “quite significant, very significant,” Kerry said, but he did not name the would-be donors.

The Obama administration is likely to have more difficulty winning passage in the House, where liberal and libertarian opposition to military engagement is stark. Kerry had an angry exchange with Rep. Jeff Duncan (R-S.C.) over what the lawmaker said was a rash decision to attack.

“Is the power of the executive branch so intoxicating that you have abandoned past caution in favor of pulling the trigger on a military response so quickly?” Duncan asked Kerry.

Kerry, who fought in Vietnam in the 1960s and voted to authorize the war against Iraq a decade ago, shot back angrily: “I volunteered to fight for my country, and that wasn’t a cautious thing to do when I did it.” When Duncan interrupted, Kerry raised his voice.

“I’m going to finish, Congressman,” he said.

Earlier, anti-war demonstrators sitting behind Kerry held their red-painted palms aloft for the television cameras. As he did when addressing senators on Tuesday, Kerry acknowledged demonstrators and said their views are welcome. He promised that the administration is not rushing to war.

Testifying alongside Kerry, Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, said Assad might respond to a missile strike with a retaliatory cyberattack. The Pentagon has planned for that and other possible after­effects, he said. The government has sent out a classified bulletin alerting certain sectors of industry of the potential for such an attack, U.S. and industry officials said.

“Those acting on the Syrian government’s behalf have already demonstrated a limited capability in cyber,” said a senior military official, referring to attacks by the Syrian Electronic Army, a pro-Assad hacker group, that disrupted the public Web sites of Twitter and the New York Times last month. The official spoke on the condition of anonymity to describe military planning.

Obama, the first sitting U.S. president to visit Sweden for bilateral meetings, came here to discuss trade issues, global development and climate change with a key European ally. But the situation in Syria hung over his visit. Obama pressed his argument for a strike by invoking the Holocaust to warn of the consequences of inaction.

Later in the day, he donned a white yarmulke and visited the Great Synagogue and Holocaust memorial, where he marked the start of the Jewish New Year, Rosh Hashanah, and paid tribute to the late Swedish humanitarian Raoul Wallenberg, who helped save hundreds of Hungarian Jews during World War II.

Englund reported from Moscow. Anne Gearan, Ed O’Keefe and Ellen Nakashima in Washington contributed to this report.