Sen. Edward M. Kennedy said yesterday he will address the Democratic National Convention next Tuesday during the platform debate on economic issues.

The announcement came on a busy day of briefings, news conferences and leaks that set forth a general schedule for the major skirmishes at the New York convention.

But what would happen after the convention ends remained unclear as a senior Kennedy aide said the "party unity" statement released jointly by the Kennedy and Carter camps Tuesday does not necessarily commit Kennedy to support President Carter if the president is renominated.

Paul Kirk, Kennedy's top political adviser, told reporters that the joint statement says only that "we'd make an effort at reconciliation." Kirk went on to say that "there could be barriers in the way" if the Democratic nominee and the party platform do not "deal satisfactorily" with economic questions.

Kennedy also announced that the major speech for his side during the rules fight will be given by Sen. George S. McGovern (D-S.D.), a Kennedy supporter and the chairman of the party committee that initiated a series of reforms after the 1968 Democratic convention that opened up the nominating process. Carter supporters say the rule McGovern will be opposing grew out of the reform movement he led.

The two campaigns also revealed that, in negotiations over the last two weeks, they compromised away their differences on five of the 18 platform planks that the Kennedy forces originally had planned to challenge on the convention floor.

Among the planks settled in the private negotiations was the platform language on draft registration. Throughout the primary campaign, Kennedy criticized the peacetime draft registration Carter called for after the Soviet invasion of Afghanistan, while the president and his surrogates defended it. Now the two camps have tentatively agreed on a platform statement saying registration is "intened" to speed up military mobilization "in the event of an emergency, which is the only time it should be used."

The negotiators also agreed to do away with floor fights on Social Security recipients' cost-or-living increases, federalization of state welfare costs, a state's right to refuse to accept nuclear waste within its borders, and gas and oil decontrol. The last issue, though, presumably will be discussed in the general floor debate on the economy.

The two sides also compromised on three of the five challenges Kennedy had planned to mount against proposed convention rules. When the rules are brought up for consideration next Monday, therefore, there will be floor fights only on the much-discussed "open convention" provision and on a Kennedy "accountability" proposal that would require any Democratic nominee to state in writing his objections, if any, to the party's platform.

The convention schedule that emerged from the extended negotiations thus provides for two major prime-time floor debates before the delegates get around to nominating their presidential candidate Wednesday.

The first, involving an hour of debate that will start about 6:30 p.m. Monday, involves the "open convention" rule. On this one, Kennedy's forces will propose a "minority report" that would permit delegates to disregard their original pledges when voting for the presidential nominee. If the Carter side wins, the majority of delegates pledged to support the president will be required to vote for him and he should be assured of the nomination.

The other rules vote, now scheduled for midafternoon Monday, may be a harbinger of the open convention vote that evening. If the Kennedy side wins on that accountability rule, it may be a sign that Carter is in trouble on the open convention rule.

On Tuesday, when the convention moves on to approving the party platform, there will be floor debate on the 13 Kennedy "minority reports" not compromised in the negotiations, and also on five other minority platform planks submitted by people independent of the two compaigns.

Most of the platform debates should be finished Tuesday afternoon, before the majority of the television audience tunes in. But about 7 p.m., the convention is scheduled to move into a two-hour floor debate on four Kennedy platform proposals dealing with the economy.

Susan Estrich, who is planning the platform debate for the Kennedy campaign, said yesterday that her side will use its time to present "a general statement on the economy, unemployment, the policies of this administration that have led to recession." Kennedy will be the featured speaker during this presentation. The Carter camp has not yet determined who its chief speakers will be.

After the debate, a roll-call vote will be taken on one of the four Kennedy economic proposals. A Kennedy victory on this vote could be embarrassing to Carter even if he goes on to win the nomination, because the platform planks Kennedy has proposed sharply criticize Carter's handling of inflation, unemployment and energy.

Kennedy announced yesterday that Rep. Barbara Mikulski (D-Md.), who has supported his candidacy from the start, will place his name in nomination in New York.

A new Gallup Poll of Democrats natinwide shows that Carter will go to the convention with less support in his own party than any other incumbent in the history of the poll.

Gallup's survey found that only 39 percent of Democrats prefer Carter as their party's nominee; 52 percent say they want "some other person." In a head-to-head contest with Kennedy, Carter leads, 47 to 43; a month ago a Gallup Poll of Democrats gave Carter a 60-to-34 lead over Kennedy.