For Europeans, it's a signal of commitment when U.S. Secretary of State Hillary Clinton and Secretary of Defense Leon Panetta are sitting together at the Munich Security Conference, the first time in the 50-year history of the forum. For Americans, they hope not only to show unity, but to create a greater sense of responsibility.

"I have heard all the talk about where Europe fits into American's global outlook. And I have heard some of the doubts expressed," Clinton said in a panel discussion on Saturday, referring to a widespread anxiety in Europe after U.S. president Barack Obama announced a "broad shift" to hug "a Asia-Pacific century" in November.

The United States' declaration of "strategic turn" to Asia was followed by concrete moves, including resetting priority of military deployment for the U.S. Army in January and a plan of withdrawing two of its four combat brigades, or 7,000 soldiers in number, from the European continent.

"There is no doubt that this change of strategy was a defining point. The period in which European democracies were American's most sought-after partnership is over," German historian Heinrich Winkler wrote in a recent article.

Facing with tens of counterparts from Europe in Munich, Clinton and Panetta made use of the annual opportunity to sing a different tune, with reassured commitment to its closest allies in the international arena.

"Europe is and remains America's partner of first resort. I have now traveled to Europe 27 times as Secretary of State. President Obama has visited 10 times," Clinton said.

When President Obama said Europe remains the "cornerstone" of our engagement with the world, "those aren't just reassuring words. That is the reality," She added.

The U.S. top diplomat then cited the joint efforts made by two sides on changing Libya, stabilizing Afghanistan and pressing Iran for its nuclear programs, adding that the traditional transatlantic ties have "never been more closely aligned in confronting the challenges of a complex, dangerous, and fast-changing world."

Panetta said that even with the calling back of U.S. troops, Europe is still the largest region that has American military residence. In Munich, he pledged to commit one U.S.-based brigade as Washington's contribution to the NATO Response Force.

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

As the United States pivots to Asian, it will need Europe more than ever, noted Anne-Marie Slaughter, a former Director of policy planning in the U.S. Department of State.

Europe, the second largest economy and military power with two out of five permanent seats in U.N. Security Council, will be a "back-up" needed for America as it looks to the Pacific, Slaughter said.

With reconfirmed commitments, U.S. officials said they expected the Europeans to share more responsibilities as a return, with many U.S. lawmakers arguing that the Europe has long been assuming Washington would get everything done and been reluctant to put money and resources into defense.

"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," Panetta said. "Let me now suggest the steps Europe must take in order to cast a similar vote of confidence."

Panetta urged European nations to keep investing crucial military capabilities of national defense and NATO to "best manage the security challenges of the future", which was apparently not a easy job as Europe is facing mounting pressure from mass budget cuts and lasting debt crisis.

He also said the European allies should continue to provide supports for the NATO-led International Security Assistance Force in Afghanistan, maintaining a long-term success in the war-torn country.