ALL WITHIN 24 hours the administration has made new arms-supply arrangements with two Asian countries, China and Pakistan, with the Red Army on their borders. The purpose of the deals is to better limit Soviet expansionism -- not simply by providing the means but by adding the encouragement the means but by adding the encouragement of friends and the supposed deterrence of foes that go with any arms transfer. At the same time, these deals deepen the American commitment to regimes of independent purpose and uncertain staying power and draw the United States further into their respective regional whirlpool. Add American efforts to strengthen Japan's defense policy: the whole American posture in Asia is being transformed.

China had previously been limited to "military support equipment" and to technology with civilian as well as military uses. Now it is being notched up the arms-supply ladder and enabled to buy "lethal weapons." They symbolic value of this step is considerable. Its practical meaning will depend on Chinese requests and American case-by-case responses evidently not yet worked out. A measured pace seems wise. Major adjustments on the Washington-Moscow-Peking triangle are deadly serious. Presumably Secretary of State Haig and his hosts in Peking agreed that the sight of expanded Sino-American cooperation would give the Soviets pause in Poland, Afghanistan and elsewhere. The trick is, of course, not to convince them inadvertently they have nothing further to gain from restraint. The way in which the new tie is knotted will be all-important. The Taiwan angle, meanwhile, remains sharp.

Pakistan was cut off from American arms in 1979 on account of its nuclear program. Subsequently it became Exhibit A in the new administration's case that "well-intentioned" efforts to influence the human rights or nuclear policies of friendly nations undercut American strategic interests. Now, just as the proliferation problem is spotlighted, a $3 billion military-economic assistance package is announced for what may be the next nuclear power. The timing is appalling, even if you accept the argument that a general security embrace will do more to slow proliferation than specific anti-proliferation pressures. Whether the new deal will end up adding to General Zia's strengths or his cares, moveover, is a question. If he is an appealing strategic bet, he is a risky political one.

In the substance of its arms-transfer policy, the Reagan administration is reversing the original Carter approach. It shares, however, a confidence that transfers can be used effectively for larger policy purposes. Watch out. Arms transfers are a well trampled field of policy. What gets trampled are the certainties each new administration brings to it.