Secretary General Kurt Waldheim of the United Nations has compared the slow-motion drama being played out in Iran to the capture of the U.S. spy ship Pueblo in 1968.

His point is that the Pueblo face-off ultimately was resolved peacefully.

But while there are important similiarities in the two cases, there are also important differences threatening to make the peaceful solution harder to find now than it was for the Pueblo.

The most significant similarity is a Third World country immobilizing the American president militarily by holding a gun to the heads of captive U.S. citizens.

As President Johnson contemplated bombing North Korea to retaliate for the hijacking of the Pueblo, he had to assume that such action might cost the lives of the 83-man crew held captive.

President Carter, as he weighs his military options, must assume that exercising them may bring death to the 50 Americans under Iranian guns in Tehran.

Johnson allowed his pride as commander-in-chief of the world's mightiest military force and left it to the diplomats to win the release of 82 of the 83 Pueblo crewmen. One died from wounds suffered in the ship's capture off Wonsan harbor Jan. 23, 1968. Negotiating their release took 11 months.

Waldheim is counseling the United States to show the same kind of patience toward Iran. "I am the first one to understand the uneasiness, the deep preoccupation of the American government and the American people," he said Sunday on "Face the Nation" (CBS, WDVM), "but I think we should not rush into something which could have disastrous consequences. And if I looked to other crises, like the Pueblo incident, it took months before a peaceful solution was found. But it was finally found."

The big difference in the Pueblo case is that the hijackers made a demand that the United States could bring itself to meet: admit that the ship intruded into North Korea's territorial waters.

And President Johnson, in the 11 months leading up to that admission, had an easier time containing the nation's anger than President Carter is having today.

For one thing, the feeling of righteous indignation about the hijacking of the spy ship was diluted by the dark suspicion that maybe the Pueblo really had violated her orders and sailed inside North Korea's 12-mile territorial limit.

Pueblo skipper Lloyd Bucher had failed to provide Washington with any reassurance on this point in his last, frantic communications from the ship under attack by North Korean gunboats. The North Koreans subsequently beat confessions out of the Pueblo crewmen that the ship had intruded into territorial waters.

Also, there were no nightly television broadcasts from Pyongyang, capital of North Korea, to remind the American people that a hostile power was holding a group of its citizens hostage.

And finally, other news -- notably of the Vietnam war -- eclipsed the Pueblo hijacking and the fate of her captive crewman. Many of their wives felt compelled to distribute "Remember the Pueblo" bumper sticker to keep the case on the U.S. conscience.

The United States won the release of the Pueblo crew by signing a statement apologizing for the ship intruding into North Korea's territorial waters. North Korea got its propaganda victory. The United States, which immediately disavowed its own statement, got its 82 Americans back.

In contrast, the Iranian militants are making a demand that President Carter cannot bring himself to meet: return the shah to stand trial.

And as the days wear on with no break in the impasse, the anger of the American public may rise and its patience thin.

Unlike the Pueblo case, the righteous indignation of the American public is undiluted by any doubts about what happened. The Iranian militants clearly broke the law by storming into the U.S. embassy in Tehran and tying up its occupants. The Pueblo, after all, was a military spy ship -- not an embassy staffed by civilians.

Families of the embassy hostages have felt no need to issue "remember" bumper stickers. Television broadcasts every night from Iran, newspaper headlines and other coverage have kept the crisis front and center. There is nothing like the Vietnam war to draw off the media.

Given the differences, it is questionable that Carter has anything like the 11 months afforded Johnson on the Pueblo to negotiate his way out of the Iranian crisis.