IN just four weeks in Geneva the Reagan administration will make the opening move in setting the tone and structure for its foreign policy achievements for its second term. Talks between Secretary of State George Shultz and Soviet Foreign Minister Andrei Gromyko Jan. 7 and 8 should bring some order to the rolling wave of hints and gestures from both sides that direct negotiations on arms control should be resumed.
On the Washington side, the administration is still split between those who insist the talks should be just about talks and no more, and those who feel Mr. Shultz should show ''some ankle,'' that is, suggest specific negotiating gambits that would indicate President Reagan is serious about wanting results.
There's nothing mysterious about what ankle could be shown. In the theater nuclear weapons, the ankle is in future deployments: first a possible slowdown in scheduling, and second some rollback of Pershing II deployments if negotiations proceed. Something like this was suggested back in 1982. Then there is the possible inclusion of the British and French theater nuclear systems as suggested in 1983. In space weaponry, the ankle is the testing issue: How would the US proceed with its testing schedule if negotiations begin?
The administration knows these possibilities and others. The internal debate goes on. The State Department allied with the White House staff is making as much of the Shultz-Gromyko meeting as it can, in effect enlarging President Reagan's stakes in the outcome and at the same time trying to moderate expectations to guard against a possible letdown. Others in the administration are still insisting that previous US proposals have been satisfactory and that the existing, though recessed, talks are adequate.
President Reagan, it seems to us, has already gotten himself deeply enough committed to the high-level communications exchange - not only between Mr. Gromyko and Mr. Shultz but between Konstantin Chernenko and himself - to have put his presidential prestige on the line. This has come about incrementally - from his campaign emphasis on seeking peace, his exchange of letters with his Soviet counterpart, to his dampening of hardliner static in recent days by excluding more confrontational advisers from White House ranks.
Chernenko and Gromyko, among the reigning Soviet old guard, have gotten deeply into the talks business too. If Washington proves an unserious bargainer, it could lead to a chill in East-West relations worse than the one from which the two sides are struggling to emerge. An episode like the intrusion of high-performance Soviet aircraft into Central America, which the Reagan administration could not permit, could again derail arms talks progress. But barring such an event, a commitment to good-faith negotiation now appears inescapable.
An administration finds it difficult to shoulder more than one major foreign policy boulder at a time. Partly for this reason, the Reagan team is playing down other regions such as the Middle East for the time being, to concentrate on the Soviets and arms. This seems wise.
Efforts are customarily made to make preparations for high-level talks, as well as actual negotiations, inscrutable. In this case, the White House has even invoked a signed nondisclosure pledge for aides involved in preparations. But eventually the gist of the internal arguments will be known, along with the President's choice among options. We trust that eventual disclosure will reflect a distinct presidential commitment to a new, positive relationship with the Soviet Union.