President Carter Warned Congress Yesterday that he will use all the powers at his command, including vetoes of spending measures he considers excessive, in pursuit of his goal of a balanced budget by 1981.

In his most direct comments to date on what is shaping up as a collision with the Democratic controlled Congress over spending, the President told a nationally televised news conference:

"I respect the Congress and I will work day and night to reach an agreeable solution to these potential threats to harmony. But I have to reserve the right and the duty to say no when spending is excessive."

Carter opened the news conference with a prepared statement, sprinkled with kind and conciliatory words for Congress, but bearing the unmistakeble tone of a threat of confrontation over spending.

He singled out three measures that he said posed a "potential problem" - an appropriations bill for water projects, the Labor and Health, Education and Welfare appropriations measure and farm price supports legislation.

In each case, the spending levels now in the bills exceed administration recommedations. Moreover, Congress not only has shown little inclination to cut the spending levels, it has in recent days including yesterday as the President spoke, added spending to the measure.

A White House official said arrived on Carter's desk at the same time, be almost certainly would not veto all three. Of the three, the most likely target of a veto is the $10.2 billion public works money bill that includes more than $200 million for 17 water projects Carter wants halted, he said.

"There's a bigger principle involved," the official said of the President's highly vocal efforts to kill what he considers wasteful water projects.

Carter's threat of vetoes came after several days of similar comments by other administration officials, including Budget Director, Bert Lance and White House press secretary Jody Powell.

The President said that he feels "very strongly" that in "a normal economy, with high unemployment, the budget ought to be balanced."

Although his own anti-inflamed proposals have been criticized as weak, Carter said his main economic concern is the rate of inflation, which he tied directly to the size of the federal budget-deficit. He warned that excessive spending now might jeopardize future administration plans for tax and welfare reform and national heatlh insurance.

The president did no confine himself to vetoes in a possible war with Congress over spending. He said he would "reserve the right to use any proper and legal prerogatives to pursue my position," including presidential authority ot impound funds appropriated by Congress.

Ironically, during his campaign Carter frequently critcized Presidents Presidents example by accusing the "Nixon-Ford administration" of govermne by "vetoes and not vision..."

After the press conference, Powell denied suggestions that the president's opening statement was an attempt to appeal over the heads of Congress directly to the people.

" If I want to write a statement to do that, I could have done a much better job," he said.

Powell stressed the "very conciliatory"aspects of Carter's statement. He said the president had told menbers of Congress the same things in private and believed that saying them in public would "add credibility" to his stance.

"He just wanted to make it clear that he is willing to take the political heat if necessary to say no on some of these things," Powell said.

On Capitol Hill yesterday, one of the three bills Carter singled out moved along the legislative path toward a possible confrontation with the White House. The House Appropriations Committee approved the $61.3 billion Labor-HEW by $1.4 billion, after rejecting by one vote a personal appeal from the President to cut $563 million from the bill. Meanwhile, a Senate Appropriations subcommittee voted to add $765 million to its version of the bill.

On other matters, the President defended the welfare proposals his administration is developing, denying that he has backed down on a pledge to relieve local governments of their welfare burdens. He said cites have already received additional aid from nonwelfare programs, and he reiterated his commitment to reform the welfare system but not increase overall welfare spending.

In response to another question, Carter declined to say whether, after he leaves office, he would accept payments for writing and television appearances. But citing the fact that he no longer receives royalties from his autobiography, "Why Not the Best," he added, "I don't want to benefit financially from this status."

Chatting with reporters after the press conference, Carter said he will ride on a nuclear submarine today in an attempt to better understand the nation's military capabilities. Carter and his onetime Navy mentor, Adm. Hyman G. Rickover, will board the submarine USS Los Angeles at Cape Canaveral, Fla., today for about a nine-hour voyage.