U.S. Army General Martin Dempsey has been sworn in as the nation's top uniformed officer.

At the event outside Washington, President Barack Obama described General Dempsey as one of the military's most battle-tested officers.

The 37-year veteran replaces retiring Navy Admiral Mike Mullen as chairman of the Joint Chiefs of Staff. Dempsey's career includes two tours of duty in Iraq, and serving as acting commander of all military operations in the Middle East.

Dempsey moves into his new role as the military faces deep budget cuts to help trim the massive U.S. debt, and also as the U.S. sees strained relations with Pakistan over that country's apparent failure to dismantle Islamic extremist groups. Mullen recently described the Haqqani terrorist network as a “veritable arm” of Pakistan's intelligence agency.

President Obama has asked the Defense Department to cut $400 billion from its budget over the next 12 years. During his confirmation hearing last month, Dempsey warned lawmakers that cuts of $800 billion or more would be “extraordinarily difficult and very high risk.”

Mr. Obama nominated Dempsey in May, only a month after the general assumed the post of chief of staff of the Army.