US prepares new concessions, new initiatives on arms.

In response to persistent Democratic criticism on arms control, the Reagan team is stepping up its efforts to appear reasonable and truly desirous of an arms reduction agreement.

Officials say this will be topic No. 1 when the President meets with Soviet Foreign Minister Andrei Gromyko next week. To prepare the soil for what obviously will be a preelection public-relations plus, senior administration officials have been dispatched this week to assert United States flexibility. Included here are some tantalizing teasers about possible new trade-offs on US and Soviet nuclear delivery systems that might be particularly appealing to the Kremlin.

''We are willing to reduce or limit those weapons which are of concern to the Soviets, if they reduce or limit their weapons which are of concern to us,'' chief US arms negotiator Edward L. Rowny says in a speech to be delivered today to the Foreign Affairs Leadership Forum in Jackson, Miss.

Interviewed by the Monitor and two other news organizations for a program to be broadcast this weekend on Voice of America, General Rowny emphasized reductions the US is willing to make in strategic bombers, nuclear-armed cruise missiles, and submarine-launched ballistic missiles.

''What's different is that in the past we have said that all these things would need to be considered,'' Rowny said in the broadcast to be heard by millions of Europeans, including Russians. ''I am now saying that we would make deeper reductions in the bombers and air-launched cruise missiles if they made deep reductions in the ICBMs.''

In later conversation, the chief US arms control negotiator also said the US would be willing to take into account NATO medium-range missiles when talking about strategic weapons (those that can reach between continents). The Soviet Union walked out of the INF (intermediate-range nuclear forces) talks when the first US-supplied Pershing II and cruise missiles were deployed in Europe. Moscow also has refused to set a date for resuming the parallel strategic arms reduction talks (START) in Geneva.

In another speech this week, National Security Adviser Robert McFarlane said, ''We are ready with flexible positions, imaginative options, and hopeful that before long we can be back at the table.''

A new and potentially complicating factor, however, will be the Reagan-inspired US effort to find ways of defending against nuclear attack from space. In his controversial ''star wars'' speech 18 months ago, the President acknowledged that ''if paired with offensive systems, they (space-based defense systems) can be viewed as fostering an aggressive policy, and no one wants that.''

Some US critics say that may be the result, if comprehensive reductions in nuclear arms are not achieved soon. The US lead in technologies applicable to missile defense apparently was one reason the Soviet Union earlier this summer offered to join new talks on banning space weapons. The US agreed to meet in Vienna (beginning this week), but Moscow pulled back when the US said it wanted to include ballistic missiles in this new arms control forum.

General Rowny suggests that the US - having demonstrated the feasibility of missile defenses - might agree not to deploy such systems in exchange for Soviet reductions in large and accurate intercontinental ballistic missiles. But some arms control experts find this unlikely.

''I think that's a very dubious proposition,'' says Gerard Smith, head of the US delegation that negotiated the first strategic arms limitation treaty (SALT I) and the antiballistic missile (ABM) treaty in the early 1970s. ''With the new star-wars factor thrown in, I don't see any prospect of our working out a deal with the Soviets on START.''

''The fact that we have not ratified the past three treaties (SALT II, the Threshold Test Ban Treaty, and the treaty limiting underground nuclear testing for peaceful purposes) has not whetted the Soviet appetite for further treaties, '' Ambassador Smith said in critiquing the Reagan record on arms control.

While being careful not to call it a unilateral ''freeze,'' Democratic presidential candidate Walter Mondale has said he would initiate a six-month ''pause'' in the testing and deployment of US nuclear weapons to see if the Soviet Union would follow suit.

Rowny rejects a nuclear freeze on the grounds that it would ''reduce any incentive the Soviets might have to negotiate the reductions we have proposed.'' And he says ''we must continue to modernize our forces (as an) added incentive to negotiate.'' At the same time, the message he is stressing this week is that ''arms control is an important matter that we take seriously.''

''President Reagan has gone farther than any other president in the breadth, the content, and the depth of his arms control proposals,'' he says. ''I, like President Reagan, want real arms control, real reductions, a real reduction of the threat of nuclear war.''