BEIJING -- The U.S. and Chinese defense chiefs took a step Monday toward mending frayed relations between their powerful militaries, though China warned ties could be cut again if Washington does not heed Beijing's wishes.

U.S. Defense Secretary Robert Gates and Chinese Defense Minister Liang Guanglie, after a morning of talks, agreed to set up a working group to explore a more formal, regular dialogue on strategic issues.

The agreement, along with Gates' visit, marks the symbolic end to a rocky year in which Beijing cut off defense ties with the United States over arms sales to Taiwan, the democratic island China claims, and objected to U.S. naval maneuvers in the Yellow Sea. Gates also extended an invitation to the chief of the People's Liberation Army's general staff to visit Washington in the first half of this year.

"I come away from these meetings convinced that the PLA leadership is as committed to fulfilling the mandate of our two presidents as I am," Gates said at a news briefing.

But the step forward on strategic talks falls short of protecting ties between the militaries from further ruptures. Liang, who is a PLA general, refused to guarantee that Beijing would refrain from suspending military ties in the future, especially if there are future arms sales to Taiwan.

Such arms sales "severely damage China's core interests," Liang told reporters after the talks. The U.S., he said, needs to pay more attention to what China wants.

Gates' four-day trip to Beijing comes a week before Chinese President Hu Jintao goes to Washington, and both governments are trying to smooth over substantial friction over trade, North Korea's and Iran's nuclear programs and China's generally more assertive diplomatic posture.

A rapid build-up of the Chinese military has added to the tensions, fueling perceptions of an aggressively rising China, unnerving neighbors and causing Washington to insist that Beijing more clearly explain its intentions.

China has made strides in building a new stealth fighter jet, and Washington is also concerned about a new ballistic missile that could theoretically explode a U.S. aircraft carrier nearly 2,000 miles (3,200 kilometers) out to sea. China has also apparently beaten U.S. estimates to develop that weapon.

Gates told reporters traveling with him to Asia on Sunday that China had the potential to "put some of our capabilities at risk."

"We have to pay attention to them. We have to respond appropriately with our own programs," Gates said.

At their news conference Monday, Gates and Liang denied their governments are entering an arms race. Liang, dressed in his military uniform, animatedly defended China's growing capabilities, calling them "entirely appropriate and consistent with China's rise as an economic and political power."