President Carter yesterday urged Congress to vote initial production funds for a new generation of neutron nuclear weapons.

In a letter to Sen. John C. Stennis (D-Miss.) chairman of the Senate Armed Services Committee, Carter said, "it is my present view . . . (the neutron weapons are) in this nation's security interest."

Carter said, "an agressor should be faced with uncertainty as to whether NATO would use nuclear weapons against its forward echelons."

"For these purposes," the President wrote, the new generation of neutron weapons "present an attractive option."

Funds for initial production of 8-inch neutron artillery shells and Lance missile neutron warheads are contained in the Energy Research and Development Administration portion of the fiscal 1978 public works money bill now before the Senate.

Sen. Mark O. Hatfield (R-Ore.) plans to offer an amendment to the bill today that would delete production funds for the neutron weapons. An earlier Hatfield attempt was halted by a 43-to-42 vote before the Senate's July 4 recess.

Hatfield has argued that Congress should not approve the money without having Carter's reasons for going ahead with production.

Carter's letter to Stennis, floor manager of the bill, was designated to blunt sentiment in the Senate for Hatfield's amendment.

At his press conference yesterday Carter conceded he had not known the neutron weapon funds were in the ERDA budget before that fact was disclosed in news stories.

But, he added, "it is not a new concept at all, not a new weapon."

The proposed neutron weapons are the first tactical nuclear warheads and shells specifically designed to kill enemy personnel by radiation rather than destroy their installation and equipment by heat and blast.

Carter told reporters yesterday, "I have not yet decided whether to advocate deployment of the neutron bomb," which, his aides later said, meant he had not made a decision on production and deployment of the weapons.

At his press conference, however, the President pointed out only positive characteristics of the new weapons. He said the destruction from neutron shells "is much less than the destructions from an equivalent weapon of other types" and that neutron warheads "ought to be one of our options."

In his letter to Stennis, he said the neutron weapons "by enhancing deterence . . . could make it less likely" that he would have to employ any nuclear weapons at all.

"The ownership of atomic weapons and their potential use is such a horrifying prospect," Carter said at his press conference, "their use . . . is a deterrent to a major confrontation between nations who posses atomic weapons."

Carter said that the "first use of atmoic weapons might very well quickly lead to a rapid and uncontrolled escalation in the use of even more powerful weapons with possibly a worldwide holocaust resulting."

That same argument has been used by Hatfield and others who say the neutron weapons, because they appear to be more accurate and less destructive, would be tempting to use in breaching the barrier between conventional and allout nuclear war.

But Carter, in his Stennis letter, called the "decision to cross the nuclear threshold . . . the most agonizing to be made by any President."

"I can assure you," Carter wrote, "that these [neutron] weapons would not make that decision any easier."

Carter refused to say under what conditions he would turn to use of tactical nuclear weapons but added his belief "that the nation that uses atomic weapons first would be under heavy condemnation from the other people in the world."

He modified that by implying that using nuclear weapons against an "unwarranted invasions" woule be permissible.

Although an arms control impact analysis was provided the White House two weeks ago, Carter said in his Stennis letter, "whether or not the weapons have significant destablizing aspects requires and will receive study" in an arms control impact statement.

Carter repeated an earlier pledge that his decision would be made shortly after Aug. 15 and if he still supports production the impact statement would be sent to Congress.

Opponents of the neutron weapons have argued Congress should have an impact statement before it votes production funds.

In setting the stage for today's debate, Hatfield charged yesterday that several neutron warheads used at the same time on a battlefield "would create a high doses of highly toxic isotopes which could endanger civilian populations."

Hatfield said he had received information from a former director of the government's Los Alamos laboratories where nuclear weapons are designed that indicated to him "our lack of solid answers to some deeply unsettling questions about the neutron bomb.

In Belgium, yesterady, NATO commander Gen. Alexander M. Haig Jr., told a news conference that the European allies had given "enthusiastic support" to the proposed tactical neutrol weapons. Haig, according to press reports, urged inclusion of the weapons in the NATO arsenal.