The United States and the Soviet Union have made unexpected progress toward formulating common guidelines to control the sale of conventional arms throughout the world and may achieve "concrete results" in a crucial negotiating session late this year, the State Department said yesterday.

Spokesman Hodding Carter said 10 days of just completed U.S.-Soviet meetings on the question in Helsinki produced "good progress" toward a meeting of minds between the super-powers, which are the two largest suppliers of weapons to the rest of the world.

Carter expressed the hope that the next round of talks, expected in December, could bring about such accomplishments as an agreed framework for controlling arms sales and perhaps some agreement on the actual implementation of restraints.

State Department sources said U.S. Soviet agreements, which could be expended to bring in arms supplier nations in Western Europe and elsewhere, are essential to the success of President Carter's policies of conventional arms restraint. Some sources suggested that the policy of unilateral U.S. restraint would have to be abandoned, perhaps as early as next spring, unless other nations can be persuaed to take similar action.

One of the central arguments of European arms suppliers, who have been unenthusiastic about controlling their weapons exports, is that any such move would be self-defeating unless the Soviet Union agreed to participate.

In fact, according to U.S. officials, the Russians have been more positive in their attitude toward control of arms sales than the Europeans.

Soviet willingness even to discuss the matter was in doubt before the first round of talks last December, and the serious attitude of the Russians in subequent meetings was a greater surprise. As a result of the recent talks, officials said, a U.S.-Soviet agreement on control of conventional arms is no longer considered almost impossible, although it still is far from being assured.

The officials would give no details of the types of control that the super-powers might adopt. However, they suggested that the restraints might follow closely some of the unilateral restrictions placed on American sales by President Carter. Among other things, these are:

Refusal to be the first supplier to introduce newly developed, advanced weapons systems into a region.

A ban on development of advanced weapons systems solely for export.

Tighter control over the retransfer of weapons by the buying nation to a third country.

These regulations do not apply to major U.S. allies such at NATO countires and Japan, and State Department officials said yesterday that the U.S.-Soviet discussions also center on sales to developing countries rather than major allies. The officials suggested that, if negotiations are successful, a set of agreed arms sales rules could be as detailed as those which have been recently adopted by the nuclear supplier countries to govern the sale of sensitive nuclear technology and equipment.

Soviet motives for cooperating in the drive to restrain armes sales are a matter of debate. One official who has been involved in the talks suggested that the Russians would like to avoid a full-scale conventional arms race with the United States which might be both costly and ultimately unsuccessful, and that the Russians therefore have an interest in keeping alive the U.S. president's policy of attempting to restrain the overseas sale of weapons.