A number of senior State Department officials tried unsuccessfully to block a strongly worded letter last week from President Carter to West German Chancellor Helmut Schmidt.

In the letter, the general thrust of which was reported in news leaks first in Germany and then here, the president cautioned Schmidt against proposing any moratorium on deployment of medium-range nuclear missiles in western Europe when he meets in Moscow this month with Soviet President Leonid Brezhnev.

High-ranking officials who opposed the letter viewed its tone and content as an unnecssary insult to Schmidt that added more strain to an already troubled relationship.

The leak of the letter's general contents made a public insult of what otherwise would have been a private one, officials add.

Schmidt, on the other hand, has lobbed a number of not-so-private insults toward the Carter administration over the years, and there could be a dose of retribution in the letter episode.

Informants say that the basic concerns laid out in the president's letter were those expressed by presidential national security adviser Zbigniew Brzezinski and Defense Secretary Harold Brown about Schmidt's position on the complicated missile question.

Secretary of State Edmund Muskie is said to have seen the letter before it was sent and did not register opposition at the time. But senior officials believe that was probably because of the secretary's relatively short time on the job. They say that Muskie was startled later by how sharp and widespread opposition was within his own department.

Despite differences between Schmidt and Carter on a number of issues in recent years, Bonn has remained among the most supportive U.S. allies. Among the questions is why the letter was sent just days before Carter was to meet Schmidt privately at the seven-nation summit in Venice and well before the Moscow trip.

The situation revolves around the major decision made by the North Atlantic Treaty Organization last December to authorize deployment of 572 new U.S.-built missiles at bases in England, West Germany, Italy, and possibly Belgium and Holland. They are meant to offset some 200 new Soviet missiles already deployed, many of them aimed at western Europe.

The West, at the time, also proposed negotiations with Moscow which possibly could lead to agreements on mutual reductions in such weapons during the three years before the new U.S. missiles will actually be ready for deployment.

The Soviets have rejected this proposal. Schmidt lent very clear backing last year to the deployment plan, despite opposition in the left wing of his own party, and he still says he supports the original plan.

But the chancellor, perhaps because of domestic political considerations, has in fact made some vague statements in recent months and weeks about a missile freeze. This has caused concern in the White House that Bonn could be wavering and that such vaguesness by Schmidt could further weaken chances that Belgium and Holland will accept the new weapons.

This undoubtedly prompted Carter's letter. However, informants say that Schmidt's position had been clarified privately beforehand and that it was clear he would not propose any formal moratorium.

LAST friday, Sen. Joseph Biden (-Del), chairman of the Senate Foreign Relations subcommittee on Europe, revealed that during a visit to Bonn he received a surprise invitation to meet with Schmidt. In nearly two hours of conversation the chancellor repeatedly stressed that Bonn would not renege on its commitments, that he didn't understand why the United States was doubting Bonn's loyalty and resolve, and that he chose the senator to deliver this message because normal communications seemed to be blocked between the two countries and relations at the highest levels were being handled through "distorted press releases."

Biden met with Schmidt last Wednesday. The letter from Carter reportedly arrived later that day or the next day.