Nine months ago, when quiet George P. Shultz replaced combative Alexander M. Haig Jr. as secretary of state, it was widely predicted that there would be a new steadiness in foreign policy, that it would be made and carried out more calmly and effectively.

Today, however, U.S. foreign pol-icy seems as stymied as ever, and there is a growing body of thought that Shultz may be too quiet, that he may not be forceful enough.

President Reagan's Middle East peace plan may be mortally wounded; Shultz leaves today to try to revive it. The Salvadoran government still seems incapable of defeating that country's leftist guerrillas and Congress seems no more inclined to increase U.S. assistance there. Arms control prospects seem grim and relations with the Soviet Union and China, if anything, seem to be worsening.

The knives have come out accordingly, not just for Shultz but also for the president's national security affairs adviser, William P. Clark, who also took up his duties little more than a year ago.

Newsweek writes about "the vacuum at State" while Time opines that Clark's main role may be to reinforce the president's rightward tendencies. It quotes an unnamed White House aide who describes Clark as "content-free." Columnists Evans and Novak say failure of Reagan's once-promising peace plan has allowed Moscow back into the Middle East.

Whether such charges are valid or not, the administration thus once again faces a serious challenge to its competency in foreign affairs.

It also faces the possibility that it could enter the 1984 campaign "without a single foreign policy success," one member of Congress noted.

"Even Jimmy Carter, who had a poor foreign policy image, had the Camp David accords, the Panama Canal Treaty and the normalization of relations with China," this member said. But others in and out of the administration defend Clark and especially Shultz, saying the first expectations when he was appointed were unrealistically high.

"Maybe people are waking up to the fact that nobody's magic," a senior White House official said.

Administration defenders say that in places like the Middle East and Central America, the United States faces long-running problems that are extraordinarily complex if not impossible to solve. They say they are working on the right issues and heading in the right direction.

But the problems also remind that the Reagan administration has less foreign policy expertise in its upper ranks than any recent U.S. government and that there remain difficulties between pragmatists and ideologues in the administration that make consensus difficult.

"The administration has gone flat along with its policies," lamented one senior State Department official recently. "Nothing is moving. There is a sense of frustration."

"What we have," he said, "is essentially a minority government" of conservatives mostly in the White House, Clark's National Security Council staff and the Pentagon "which is more interested in position-taking than in problem-solving. The ideological position is what's important, not governing" and when that is combined with lack of experience "it becomes so, so hard to get things done."

The administration's two most experienced people in foreign policy, Haig and former national security affairs adviser Richard V. Allen, were forced out of office. Shultz, as Haig's replacement, has some experience but is primarily an economist. He brought in as his deputy Kenneth W. Dam, an able administrator and ex-university official, but also without much experience.

Reagan had virtually no foreign policy experience when he took office. Nor did Defense Secretary Caspar W. Weinberger or White House adviser Clark who replaced Allen.

Furthermore, Shultz and Clark have been almost invisible to the public and rarely on record before the press. This has produced another unique situation that contributes, fairly or not, to a public sense that the administration is without leadership in this area.

In the Nixon, Ford and Carter presidencies, the United States always had a secretary of state or national security affairs adviser--Henry A. Kissinger, Zbigniew Brzezinski--who was a major figure on the national and international stage.

Shultz's preference for staying out of the news and his low-key style has had some advantages until now. It has allowed him to work more effectively as a problem-solver in a highly ideological administration without attracting the ire of the right wing in the White House or Congress.

He is widely credited, soon after taking office last summer, with having skillfully turned the White House away from its policy of applying sanctions to the European allies for their participation in the Soviet natural gas pipeline project. If relations with the allies are still strained, they are probably a lot less so than they would be were it not for Shultz, who is widely respected in Europe.

Shultz the economist has also played a important role in reshaping and possibly softening somewhat the administration's other international economic policies.

He was influential in the development of Reagan's Middle East peace initiative last September and is said by aides to have a key part as well in moving Reagan to offer an interim arms control proposal to the Soviets earlier this year.

But other officials say Shultz did not have that much to do with the arms proposal and that, while increasing his involvement in arms control, is still not a major factor and has left that issue largely in the hands of the White House.

Similarly, it seems he has not played a major role thus far in Central American policy, with the more hard-line Clark and U.N. Ambassador Jeane J. Kirkpatrick taking the lead. And in the Middle East, it also is not clear how much he has involved himself until now.

Shultz is a methodical man, an academic who consults the wise men in every field and likes to prepare himself fully even before deciding if he will become involved in an issue. It is this quality, admirable in one sense but bureaucratically dangerous for a secretary who came into office with a world of troubles and half the term already over, that seems to be at the root of Shultz's difficulties.

In addition, he seems much more interested in some subjects, such as economics, than others.

White House officials scoff at criticism and describe Shultz as "very strong and into everything." But Shultz is so low-key that he seldom divulges news even at a news conference, has not created yet a public impression that he has strong ideas as opposed to skills in mediating conflicts. Shultz is a conservative who appears to be more moderate than Clark or Weinberger. But no outsiders know.

Officials who have watched him closely but who are not tied to him remain impressed by the job he is doing under the circumstances.

"You can have ideas when the world is willing to listen," said one official. "Henry Kissinger had a lot of ideas about Russia and China but none about Vietnam," he said, "so ideas are only good when you have a situation where they can be used. The world today is not the world of headlines and fundamental solutions. The Middle East will remain a problem after George Shultz's grandchildren are secretaries of states."

Besides, he and other officials add, "We are not losing in foreign policy. The Russians are running scared in Afghanistan and eastern Europe and all is not lost in El Salvador." Shultz, they add, inherited problems with China caused earlier by Reagan's fondness for Taiwan and the secretary's recent trip there reportedly had some calming effect on a worsening situation.

Policy in Africa is viewed as a plus thus far, largely because nobody knows much about it except the relevant senior State Department officials and it has been kept out of the limelight. In the White House, Clark is even more invisible than Shultz is at State. But that is the way both Reagan and Clark want it and the national security affairs adviser has no official public role to play. What is at issue is Clark's behind-the-scenes role.

But here, too, his invisibility makes it hard to gather a balanced appraisal of this powerful official. He is closer to Reagan than any other foreign policy aide and the most unschooled occupant in national security affairs ever to hold that post.

Clark holds no press conferences, is surrounded by aides who seem totally loyal and tight-lipped.

He is faulted by critics for poor judgment in pushing a controversial nominee to head the arms control agency and taking several confrontational positions lately. But he appears also to have improved the machinery of the security council staff and officials say he is meticulous about putting all options in front of the president.

Clark is also given high marks for knowing how to bring the president around on certain issues.

But Clark is so close to the president, such an ideological soulmate and spends so much time with him that his inexperience and lack of historical depth still trouble many career officials. His influence is unquestioned. But as Time magazine asked: "influence for what?"

There is also this fact, one member of Congress said: the administration has faced no truly dangerous crisis in foreign affairs. That is when the depth of foreign policy management would be tested. "So far," he said, "we've been lucky."