Democratic presidential candidate Sen. Edward M. Kennedy (D-Mass.) tried again today to entice President Carter into a debate, but the Carter campaign responded the same way it had to a similiar Kennedy effort two weeks ago: no deal.

In a speech before the Cleveland City Club, Kennedy promised to release all Democratic National Convention delegates pledged to him if Carter agrees to a debate anytime before the balloting at the August Democratic National Convention.

"I hope Mr. Carter will do the same," Kennedy said. "The convention should be at liberty to nominate Mr. Carter, to nominate me -- or to select a third person."

Kennedy is almost certain to go to the convention a distant second to the president in delegate count, no matter what happens in primary elections next Tuesday in eight states where 696 delegates are at stake.

Thus, Kennedy noted that, "It is harder for him to accept this proposal than it is for me to make it." He learned how right he was within two hours as Carter's campaign manager, Robert S. Strauss, brusquely rejected Kennedy's suggestion.

"We're debating Reagan right now, "Strauss told reporters on Air Force One heading to Columbus. "I would see no reason to debate [Kennedy]. I don't think there would be any interest in it."

Kennedy's new debate proposal was a variation on his offer two weeks ago to withdraw from the Democratic race if there were a debate before the June 3 primaries and Carter still won the most votes that day.

The new Kennedy offer was made partly for media consumption. The Kennedy staff scrubbed a foreign-policy speech they had originally planned to give here so that the president would be faced with a new Kennedy challenge as soon as he arrived in Ohio today on his own Cleveland campaign trip.

But today's speech also seems to be apublic manifestation of private efforts by the Kennedy camp to arrange a quick and peaceful end to the Democratic contest if Kennedy does not score well next Tuesday.

Within the Kennedy camp, Kennedy's debate offer is viewed as an olive branch taht would give Kennedy a dignified exit from the race and give Carter a quiet two-month period to unify the party before the convention. But the proffered branch has been treated like poison ivy by the Carter people.

Kennedy's speech today was rich with what are generally called "thinly veiled threats" of turmoil at the convention if Carter refuses to debate.

Noting that all Republicans have united behind the party's apparent nominee, Ronald Reagan, Kennedy observed that the party's situation was distinctly different than the Democratic side. "All of them can accept the outcome," he said, "because each candidate had a chance to be measured against the other."

Kennedy attacked Carter today in language at least as tough as any used by the president's GOP challengers. "He converted his foreign policy mistakes into political triumphs and he cloaked himself in patriotism," Kennedy said. "It is no wonder that Mr. Carter is afraid to debate . . . the only record he has to offer is record inflation, record interest rates, record unemployment . . . and record setbacks in foreign policy.

"A rose curtain has descended across the 1980 campaign. And from behind that curtain, the president has put forth his message of malaise . . "

Kennedy spoke today as if the debate question were the central issue of the 1980 election. As he described things, the primaries next Tuesday should be viewed not as a choice of Kennedy Vs. Carter but "as a referendum on whether Democrats want a fair debate . . . "

The candidate, whose fatigue was evident in the deep brown circles under his eyes and his quiet demeanor, began his remarks with words of sorrow about the shooting of civil rights leader Vernon Jordan the night before.

The last time a Kennedy addressed the Cleveland City Club was in 1968, when the current candidate's late brother, Robert F. Kennedy, spoke here. He addressed the organization on the morning after the Rev. Martin Luther King Jr. was assassinated.