In the high-stakes foreign policy poker game Jimmy Carter is playing with the Kremlin, China is the wild card. But there is disturbing evidence that Carter may be overplaying his hand, a risky bluff that could, in the long run, escalate a spiraling world arms race.

Carter partially inherited his hand from Richard Nixon and Henry Kissinger, and is playing it out under the guidance of Zbigniew Brzezinski.

Brzezinski is so concerned with the Soviet threat to American security that he is willing to provide sophisticated arms and technology to the Chinese. The backfire potential of this strategy is causing concern on Capitol Hill and in the U.S. intelligence community.

The concern isn't that the China overtures don't have merit, but rather that Carter's lieutenants may be stumbling down a thorny path that hasn't yet been fully explored and that could have dire implications among the Big Three of East and West.

There's no doubt that the Carter administration is willing to back up its diplomatic friendship with China with expensive military hardware. The recent visits to Peking of Defense Secretary Harold Brown and his deputy, William Perry -- each bearing a salesman's list of attractive technological items -- make this clear.

Banning Garrett, of the University of California, recently told investigators for Rep. Lester Wolff (D-N.Y.) that U.S. plans for arming the Chinese have been one of the best-kept secrets in Washington. This is despite the fact that one expert, according to Garrett, estimated the ultimate cost of arming the Chinese at a minimum of $50 billion.

Not that the Chinese are helpless militarily, by any means. "China has only a limited ability to project force beyond its borders," according to a Joint Chiefs of Staff report. But "the People's Republic is developing increasingly capable strategic nuclear and general purpose forces. . . ."

Military strategists started eight years ago to assess the possibilities of future military relations with the Chinese. In a confidential study written in 1974 by an employee of the Rand Corporation, the author, Michael Pillsbury, now a Senate staffer, composed his analysis after private, unofficial meetings held with senior Chinese military officials at the United Nations. Pillsbury told my associate Jack Mitchell he was "astonished" to learn that the Pentagon had released the confidential report of his findings.

Carter administration officials have dismissed speculation about such secret plans for Chinese-American cooperation as nothing more than "think pieces" designed to cover any eventuality, however farfetched.

But despite official downplaying, the administration's actions indicate that many specific moves toward a close military relationship with China have been implemented piecemeal since 1978. These include the sale to China of high-technology items that could have military application as well as non-lethal military equipment.

By making the relationship so clear to Moscow, Kremlinologists fear Carter may have thrown away the advantage the United States gained by its overtures to the People's Republic. Instead of playing off the two communist rivals against each other, Carter may persuade the Kremlin that the United States is irrevocably committed to China.

If that view does indeed prevail in Moscow, the Soviet leaders would see nothing to be gained by wooing the United States away from Peking. Instead, they would take action to thwart what they perceive as a Sino-American effort to strategically encircle the Soviet Union.

Government sources admit that the "tilt" toward Peking risked offending the Soviets, and was a major concern of the secret policy planners. But the "China hands" won the argument, over the objections of senior State Department experts.

Beyond the implications for detente, of course, there are expert observers in Congress and the intelligence community who question the wisdom of supplying so much technological hardware and training to the Chinese that it would be impossible to retreat from the alliance if the Chinese suddenly decide to turn their backs on their American partners.