Sen. Edward M. Kennedy (D-Mass.) went before his own people today and all but guaranteed he will challenge President Carter for the presidency.

Speaking to 800 labor union members who had just adopted a resolution urging him to run for president, Kennedy promised an answer on his intentions "in the not too many days and weeks ahead" and added: "And I don't think you'll be disappointed."

He coupled that suggestion with rhetoric that evoked memories of John F. Kennedy's 1960 presidential campaign, calling for "action on the great unfinished agenda before this country" and the "restoration of the United States as the real champion and the leader of the united free world."

In the atmosphere, any lingering doubt that Kennedy will seek the Democratic presidential nomination next year vanished almost entirely. Entering an ornate meeting room of an aging downtown hotel, he was greeted by members of the Massachusetts AFL-CIO who stood on chairs clapping and shouting, "We want Ted."

Obviously enjoying the scene, Kennedy toyed with his audience, remarking after he had been presented with a T-shirt bearing the words "Kennedy in '80" that he had been looking "for something nice to wear in the United States Senate."

Beneath the joking and campaign-style hoopla, one message seemed clear -- having deliberately raised expectations so high, Kennedy has left himself with virtually no way to back out of the race without disappointing his most fervent supporters, which include, as he noted today, the labor unions of his native state.

Missing from today's performance was any suggestion of what the Massachusetts Democrat would propose as alternatives on those subjects are certain to grow as Kennedy moves more rapidly toward an open candidacy. But for today, he satisfied his wildly enthusiastic audience with a broad condemnation of the state of the U.S. economy and, by implication, -- the administration's handling of it.

In traveling the country, Kennedy said, he has found that people everywhere "can't understand why prices are going up through the roof and why their wages are held down."

"I find that people really wonder why we can't have action on these problems," Kennedy said. "There are those voices in this country today that would have us believe that we cannot come to grips with the leading problems that we are facing in our nation, that somehow the problems of the recession, the problems of inflation are too complex for us in this nation of ours to come to grips with. "Well, I don't believe that to be the case."

Recalling the Depression of the 1930s, he added: "We did not say that that is too complex or too difficult, that somehow the American people were in a malaise. We said let's roll up our sleeves and go out and lick the problems."

Kennedy said no one has a "magic solution" to the problems of recession and inflation. But raising what has become the code word for his differences with Carter, he said that to overcome these problems "It is going to take leadership, it is going to be the same kind of spirit that has been demonstrated in this state and this country time in and time out."

Kennedy did not mention Carter by name during the speech. But he did make specific criticisms of some administration policies, charging that the president's decision to decontrol oil prices was handing over "unconscionable profits" to the oil industry.