U.S. officials said yesterday that they were encouraged by the relatively subdued nature of Arab reaction to the military confrontation with Libya because the administration had expected a more vitriolic condemnation of the United States.

"It's still too early to tell, but we feel that the reaction is not nearly as bad as it could have been," said a senior State Department official, who asked not to be identified. "In the medium term, we're hoping that the impact on our relations with Arab states will be nothing worse than a wash and that it might even boost our stock with anti-Libyan Arab governments by making them feel the United States finally stopped posturing and did something."

He and other officials stressed that the effects of the Gulf of Sidra fighting should be assessed on two levels. "We knew all along that the principle of Arab brotherhood would come into play and that even our best friends among the moderate Arabs would feel obliged to criticize us," the senior official said.

While acknowledging that the U.S. action could cause temporary embarrassment for moderate Arab leaders, the officials contended that most Arab governments privately regard Libyan leader Muammar Qaddafi as unstable and untrustworthy and thus are unlikely to give him more than superficial support.

The officials noted that Arab League foreign ministers, who met yesterday in Tunis and adopted a resolution condemning the U.S. action, turned aside Libyan calls for tougher language and for specific moves such as economic sanctions against the United States. In addition, they said, several ministers tempered their votes for the resolution with public reservations stressing their governments' desire that the U.S.-Libyan dispute be resolved peacefully.

The officials also noted that there have been no anti-American demonstrations in Arab countries other than Libya. While conceding that it is too early to rule out the possibility of violent reactions by Arab masses, the officials noted that a U.S. clash with another radical Arab state such as Syria, or even a non-Arab Moslem country such as Iran, would have triggered immediate demonstrations and attacks on U.S. outposts throughout the Middle East.

The officials said that when the Gulf of Sidra exercise was being planned, the administration's calculations about how the Arab world would react to a U.S.-Libyan clash were influenced heavily by the belief that Qaddafi's fellow Arab leaders view him with wary ambivalence and would not rush to his aid in a way that involved serious tensions with Washington.

The officials said that even if a harsher reaction resulted, the exercise was staged at a time when the United States is not involved in major Mideast initiatives that could have been undercut. U.S. hopes for reviving the Arab-Israeli peace process are at a standstill, and the other major American concern in the region -- halting the Iran-Iraq war and its threats to the Persian Gulf -- seems distant from the U.S. dispute with Qaddafi.

According to the officials, another important factor in the decision to proceed with an exercise that was likely to result in fighting was the belief of many senior U.S. policymakers that some Arab states privately wanted to see Qaddafi humbled militarily. These policymakers also are known to have argued that the Reagan administration was in danger of losing credibility in the Middle East if it failed to make good on its threats to punish one of the region's principal supporters of terrorism.

That view was disputed yesterday by many Arab diplomats here, including some whose governments are strongly anti-Libyan. The diplomats, who asked not to be identified, said the predominant view in Arab political circles is that episodes such as the Gulf of Sidra clash are more likely to inflate Qaddafi's importance in the Middle East and encourage him to incite more terrorism and unrest.

This opinion is known to be shared privately by many State Department officials and outside experts on the Middle East. The senior department official said: "What Qaddafi will do in the aftermath of this week's events is something we're frankly nervous about. But whether it means more terrorism or whether it will turn out to have been a cautionary lesson for him is something that we don't yet know."