Chuck Hagel started his work Wednesday as U.S. secretary of defense, pledging to accelerate Washington's renewed focus on the Asia-Pacific region and promote partnerships with other nations on global security.

"I've always believed that America's role in the world is one that -- and we've had variations of this throughout history -- has been one that should engage the world," Hagel said, addressing Pentagon officials at its building on the outskirts of Washington.

The former Republican senator's comments are in line with the Obama government's pursuit of strengthening partnerships with other countries in resolving international problems.

The Vietnam War veteran won confirmation from the Senate on Tuesday after a bruising, drawn-out struggle. Some Republican senators took issue with his views on Iran and Israel and his criticism of the George W. Bush administration's handling of the war in Iraq.

In a written message to department personnel later, Hagel emphasized the need to pay more attention to the Asia-Pacific region.

"As we turn the page on more than a decade of grinding conflict, we must broaden our attention to future threats and challenges," he said. "That means continuing to increase our focus on the Asia-Pacific region, reinvigorating historic alliances like NATO, and making new investments in critical capabilities like cyber."

Hagel succeeded Leon Panetta as the U.S. defense chief and faces a host of challenges at home and abroad.

His department is under growing pressure to slash budgets. In Northeast Asia alone, the Pentagon has to deal with China's increasing military influence, its territorial tensions with Japan, and North Korea's nuclear and missile threats. (Yonhap News)