The resignation of Soviet foreign minister Eduard Shevardnadze has raised concern about the imminent completion of a new U.S.-Soviet treaty limiting strategic nuclear arms, despite Soviet assurances that the agreement still can be signed at a summit meeting in early February, U.S. officials said yesterday.

The departure of Shevardnadze, who overcame his unfamiliarity with the topic to become an important and respected figure in nearly every strategic arms negotiating session of the past five years, comes at crucial moment for the eight-year-old talks, the officials said.

Tentative agreements have been reached in the last two months on the principal issues blocking completion of the mammoth new treaty, enabling Shevardnadze and Secretary of State James A. Baker III to announce the February summit plans during meetings in Houston last week.

But most of the accords were marked by what one official described figuratively as "a handshake" between the two men, rather than agreed treaty language. The U.S. officials said they feared that with Shevardnadze's withdrawal, these agreements might vanish under pressure from resurgent Soviet military officers who have differed with Shevardnadze in the past.

"I don't think it's good," a senior official who closely monitors the negotiations said of Shevardnadze's move. "But I don't think we'll know for a while whether it's a minor bump or a big hill. Are we sorry he's gone? The answer is yes."

The willingness of Gorbachev and Shevardnadze to embrace a substantial reduction in Soviet thermonuclear weapons -- the principal source of their nation's claim to superpower status -- has been frankly admired by U.S. officials, several of whom described the foreign minister as a "problem solver" who in private sessions either "pushed to the edge of his instructions from Moscow or rushed to get better instructions" after U.S. complaints.

No one on the U.S. negotiating team considered Shevardnadze a pushover, one official said; rather, he had an acute understanding that a willingness to reduce the strategic, or long-range, arms considered most threatening by the West could result in a positive transformation of U.S.-Soviet relations. The 600-page draft treaty bears the imprint of this philosophy and cuts more deeply into the number of Soviet nuclear arms capable of striking the United States than into U.S. arms that can hit the Soviet Union.

But the clash between the Soviet Union's foreign policy and arms control goals and the preferences of its military leaders became particularly noisy and public as the negotiations entered a final phase this year.

The biggest blowup occurred after a February session with Baker in Moscow, where Shevardnadze and Gorbachev military adviser Sergei Akhromeyev went "well beyond their instructions" and accepted U.S. proposals for limiting nuclear-tipped cruise missiles carried by strategic bombers, according to a Communist Party Central Committee source who did not want to be identified.

Foreign ministry officials later told their U.S. counterparts that revelation of the concession prompted a mini-revolt by Soviet Defense Minister Dmitri Yazov and armed forces chief of staff Mikhail Moiseyev that was deeply embarrassing to both Shevardnadze and Akhromeyev, who was Moiseyev's predecessor. Although Akhromeyev later denied any split, Soviet negotiators promptly withdrew the concession and hardened their positions on other issues.

Eventually, most of the U.S. positions prevailed. But the entire negotiating process was significantly slowed, causing Gorbachev and President Bush to miss their year-end deadline for the accord.

Meanwhile, Shevardnadze and the Soviet military continued to feud over other arms control issues, with the foreign ministry making it known in April that the generals had failed to disclose the transfer of short-range ballistic missiles to East European nations during U.S.-Soviet negotiations aimed at abolishing the weapons. It was a measure of Shevardnadze's credibility in Washington that the explanation was immediately accepted.

In Houston last week, Baker and other U.S. officials presented Shevardnadze with detailed evidence from U.S. intelligence assets that the Soviet military had substantially, and perhaps deliberately, understated the number of its conventional armaments subject to destruction under an East-West accord signed by 22 nations in November.

U.S. officials say the unusual disclosure was a measure of their respect for the Soviet minister, as well as a demonstration of Washington's sense of the yawning gap between Shevardnadze and his nation's military.

Early this week, prior to Shevardnadze's announcement, U.S. Ambassador to Moscow Jack Matlock delivered a letter from Baker to the foreign minister summarizing the U.S. view of strategic arms breakthroughs achieved at the Houston meetings, covering monitoring of spare ballistic missiles, inspections of strategic bombers and the broadcast of electronic data during strategic missile tests.

Soviet deputy foreign minister Viktor Karpov, who received the letter and read it in Matlock's presence, did not provide an ironclad assurance that Moscow agreed, while hinting at the government changes to come, several sources said.