The Reagan administration is using a combination of written and spoken proposals at the Geneva talks on limiting long-range nuclear missiles in an attempt to appear more flexible and evoke new ideas from Moscow on how to reach agreement.

As part of that strategy, the administration took what officials describe as an unusual step July 8 when it submitted a draft treaty at the Strategic Arms Reduction Talks (START).

Although the draft calls for the sharp overall missile reductions the administration has continually demanded from Moscow, officials said that the White House intentionally omitted language demanding that the Soviets make cuts in specific types of missiles.

Instead, U.S. negotiators orally laid out three options for Moscow to consider as ways to reduce the overall atomic striking power, or "destructive potential," of each country's long-range missiles and bombers to bring that power into rough balance.

These options retain some of the toughest and most specific demands the administration has made since the talks began in June, 1982.

But the spoken proposals also include an option that essentially calls on the Soviets to say how they would deal with the central U.S. concern--how to limit the Soviet force of big multiple-warhead missiles for which the United States has no counterpart--if they don't like Washington's ideas.

The U.S. negotiating strategy, as explained by officials here, is meant to do several things.

By leaving open the language in the draft treaty, the Americans are trying to convince the Kremlin that they are flexible about finding a way to narrow differences. They are also trying to maneuver around a Soviet complaint that the United States is attempting to dictate which missiles the Soviets could have.

At a news conference here Friday, Edward L. Rowny, the United States' chief START negotiator, said that the added flexibility President Reagan has given him in the latest round of negotiations has enabled the United States to respond to this Soviet complaint.

At the same time, the absence in the draft treaty of some specific demands that Moscow previously suggested are not negotiable may keep moderates in Congress who are reluctant supporters of Reagan defense and arms-control policies from openly turning against those policies.

But the oral options suggested by the U.S. team retain all of Reagan's initial proposals, with some modifications. Thus, at this point nothing big has been dropped from the U.S. stance, which officials said remains tough.

Here is how things stand, the officials said:

In 1982, Reagan proposed that both sides reduce their arsenal of nuclear missile warheads by about one-third to no more than 5,000 each. He also said that no more than half of these should be on land-based missiles, which are the most accurate and, therefore, the most threatening.

Privately, the administration also proposed that Moscow cut its force of some 800 SS17, SS18 and SS19 medium and heavy multiple-warhead missiles to no more than 210 and that no more than 110 of these be the 10-warhead SS18s.

These proposals, however, were not submitted in draft treaty form. In July, the White House put forward such a draft, which retains the 5,000-warhead limit but makes no mention of the 2,500 sub-ceiling for land-based warheads or the 210-110 limits on specific missiles.

However, the administration, as Rowny pointed out, remains committed "to reduce, over time, the three-to-one Soviet advantage in nuclear destructive capability and potential" represented by these big missiles.

To accomplish this, it has offfered the three spoken options to fill in the blanks of the treaty and has asked Moscow to pick one.

The first is to agree to the initial Reagan sub-limits on land-based warheads and the 210-110 limit on big missiles.

T second is to agree to limits on the overall throw-weight, or lifting power, of the rival forces. The Soviets have a big edge in this category, which measures how much atomic punch either side can hurl.

The Sovave been reluctant to give up that edge, and the recent U.S. modification is to not specify that the new limit must be lower than the current U.S. throw-weight level. Thus, Moscow may not have to reduce so much, and the United States could build up some but probably would not.

If those two options are unacceptable, the third option is for the Soets to come up with a plan that addresses Washington's worries.