MUNICH, Germany — The Obama administration on Saturday called for stepped-up U.S.-European co-operation to isolate tyrannies such as the Assad regime in Syria, promote democracy in the Arab World and beyond, and repair damage from the global financial crisis.

And, as America shifts its primary strategic focus to Asia and reduces its military presence in Europe, President Barack Obama's top two national security aides -- attending an international security conference together in a demonstration of Washington's resolve -- reassured the continent that it remains deeply relevant to U.S. interests as well as its partner of "first resort" in dealing with global hot spots.

U.S. Secretary of State Hillary Rodham Clinton said Americans and Europeans must send a clear and common message to tyrants that they must respect the rights of their people.

She spoke as violence flared anew in Syria before a vote on a U.N. Security Council resolution backing an Arab League peace plan that called for Syrian President Bashar Assad to step down. It was vetoed by both Russia and China.

"As a tyrant in Damascus brutalizes his own people, America and Europe stand shoulder to shoulder," she said, referring to Syrian President Bashar Assad.

"We are united, alongside the Arab League, in demanding an end to the bloodshed and a democratic future for Syria," she said.

President Barack Obama, in a strongly worded statement Saturday, condemned Assad's "unspeakable assault" and called for his ouster.

"Assad must halt his campaign of killing and crimes against his own people now. He must step aside and allow a democratic transition to proceed immediately," the president said.

Clinton said, "Wherever tyrants deny the legitimate demands of their own people, we need to work together to send them a clear message: You cannot hold back the future at the point of a gun."

Despite last-minute meetings on the sidelines with Russian Foreign Minister Sergey Lavrov, Clinton was unable to change Moscow's mind about the resolution.

Lavrov told the conference the resolution made too few demands of armed groups opposing Assad's regime. He also said Moscow remained concerned about whether it prejudges the outcome of a national dialogue among political forces in Syria.

In other remarks, Clinton said that while promoting democracy, Europe could not ignore backsliding in its own backyard, decrying limits being placed on press and religious freedoms. She did not identify trouble spots by name but was referring to Russia, Belarus and Hungary.

"It is not credible to preach democracy elsewhere unless we also protect it within our community," she said. "The trappings of democracy are not enough."

Clinton said she had no doubt that Europe would overcome its economic woes. But she said it is imperative for a common agenda and enhanced co-operation to reinforce recoveries on both sides of the Atlantic.

"We are confident that Europe has the will and the means to cut its debt, build the necessary firewalls, create growth, and restore liquidity and market confidence," she said. But, she added: "As Europe emerges from crisis, we have to work harder to reinforce each other's recoveries. As deep as our economic relationship is, it has not yet lived up to its potential."

To boost the recovery, she said the United States and Europe need to team up to fight unfair trade practices.

Meanwhile, U.S. Defence Secretary Leon Panetta said Europe is America's security partner of choice for military operations and diplomacy around the world. He said Europe will continue to be a central U.S. defence interest, even as the administration withdraws two of the four Army brigades stationed on the continent.

In his remarks to the conference, Panetta emphasized the positive. He noted that the U.S. is building a missile defence system in Europe, including a radar installation in Turkey and missiles to be stationed in Romania and Poland. He said four U.S. ships capable of shooting down missiles will be stationed at Rota, Spain.

And he said that while two Army brigades will leave Europe, that will be partly offset by a new arrangement in which smaller Army units will rotate to the continent for temporary training assignments. This was announced in January as part of a new U.S. defence strategy.

These changes, he said, amount to a U.S. "vote of confidence" in the future of NATO.

Panetta's remarks were aimed at countering a perception that the administration's added focus on security challenges in Asia and the Middle East is weakening U.S. partnerships in Europe.

"In all, the steps Europe can expect from the United States amount to a vote of confidence from Washington in the future of the alliance, especially in a period of fiscal austerity," he said.

He noted that the U.S. military will still have a larger presence in Europe than in any other region of the world.

"That's not only because the peace and prosperity of Europe is critically important to the United States, but because Europe remains our security partner of choice for military operations and diplomacy around the world," he said.

NATO Secretary General Anders Fogh Rasmussen said on the sidelines of the conference that he "warmly welcomed" the new U.S. plans to rotate a battalion-size force into Europe to train with other allied forces.

"It's a testament to a continued strong American commitment to European security," Fogh Rasmussen said. "Furthermore it's a significant contribution to ... joint exercises, training, education that cannot only maintain but further improve the ability of our forces to work together."

The Obama administration has sought to limit the diplomatic fallout from its decision to pull the Army brigades out of Europe -- a move in line with an overall shrinking of the Army from 570,000 soldiers to 490,000. One brigade is scheduled to pull out of Europe in 2013 and another in 2014.

Missile defence will become a central feature of the U.S. military presence in Europe. Officials in recent days confirmed that the missile defence system's headquarters will be at Ramstein air base in Germany.

Panetta also spoke optimistically about the outlook for stability in Afghanistan, where the Taliban insurgency persists.

He said the U.S. hopes Afghan security forces will be ready to take the lead combat role throughout the country "sometime in 2013." At that point, U.S. and NATO forces will shift to a support role, he said, while remaining prepared to engage in combat if necessary.

At the conclusion of the NATO defence ministers meeting he attended in Brussels on Thursday and Friday, Panetta said there is a broad consensus among the allies that 2013 should be the year for such a transition out of a lead combat role. But France takes a different view, arguing that international forces should withdraw all combat forces from Afghanistan next year.

Fogh Rasmussen said there is "no accelerated timeline" but that all responsibility could be turned over to Afghan forces by the end of 2013, even though NATO forces would stay through the end of 2014.

"From the date when you hand over to when the transition has been fully implemented it may take between 12 and 18 months, so if we are to complete transition by the end of 2014 we have to hand over the last provinces quite some months before and it may be in 2013," Fogh Rasmussen said.

"Even if we hand over the last provinces and districts in 2013, which may very well be the case, we will stay and we will also stay and conduct combat operations throughout the transition period to the end of 2014."