The United States is prepared to give assurances to the Soviet Union that it would negotiate with Moscow any proposed deployment of new defensive strategic weapons, and would give "five to seven years' " notice before deploying such weapons unilaterally, according to Defense Department sources.

These proposals, agreed to secretly at an Oct. 4 meeting of senior administration officials, are intended as a response to Soviet demands for concessions on President Reagan's Strategic Defense Initiative (SDI), the sources said. They would not have any effect on continuing research and testing of possible "Star Wars" weapons, but would delay the deployment of such weapons, presumably to give the Soviets a chance to deploy comparable systems if the United States decided to withdraw from the existing Antiballistic Missile (ABM) Treaty, which outlaws such deployments.

[White House officials said yesterday that President Reagan would be raising the issues of human rights and "Soviet expansionism" at the United Nations this week, in an effort to put the Soviets on the defensive prior to the Nov. 19-20 summit meeting in Geneva. A senior official listed arms control fourth among the administration's objectives for the summit.]

The proposal agreed to Oct. 4 by the Special Arms Control Policy Group (SAC-G) of top officials responsible for arms control policy is to offer to amend the 1972 ABM treaty, which currently provides that either superpower can withdraw from it on six months notice. That could be extended to five to seven years under this new U.S. idea.

At a hearing before a House Foreign Affairs subcommittee yesterday, Paul H. Nitze, special adviser to the president and secretary of state on arms control, said that [the SDI] "research program is not on the table. But with respect to other aspects of the program, of course [they are] on the table."

The new proposal for trying to reassure the Soviets was adopted as part of the administration's review of its position on the SDI in connection with the ongoing Geneva negotiations and the upcoming summit between Reagan and Soviet leader Mikhail Gorbachev.

The Soviet leader, who has repeatedly called for the United States to abandon the SDI program, has stated that he is prepared to permit "fundamental research" on space-based defense but not field testing of models or prototype weapons.

The new proposals for reassuring the Soviets were adopted at the same meeting where officials discussed adopting a new, expanded interpretation of what the 1972 ABM pact permits in the way of testing and development of Star Wars weapons. Since then administration officials have said that although they think a broad legal interpretation of the treaty is justified -- a position the Soviets have sharply challenged -- they will stick to a previous, much narrower interpretation.

Addressing this issue at yesterday's hearing, Nitze sought to reassure subcommittee members that the new, "broader interpretation" of what the 1972 ABM pact permitted would not be applied to the administration's SDI research program.

Instead, he said, the currently planned research "will continue to be conducted in accordance with a restrictive interpretation of the treaty's obligations.

Former ambassador Gerard C. Smith, who helped negotiate the ABM pact, told the subcommittee that although the administration had reverted to a restrictive interpretation, "it is also clear that the administration feels free under the new version to alter the SDI program any time that would appear advantageous."

Smith was sharply critical of the decision to "float this new treaty version just six week before a summit at which the ABM treaty was expected to be an important part."

He suggested an explanation may be that "it was a bargaining ploy looking to a summit accommodation somewhere between the Soviet pre-summit position of no research at all and the Reagan new version of no limits on strategic defense development."

One of Nitze's observations to the subcommittee seemed to give support to that view. When one congressman raised the prospect of an amendment requiring the administration to stick to the restrictive interpretation of the ABM treaty, Nitze responded that "if Congress limits the executive branch, then it is not necessary for the Soviets to make any trade with the United States on this issue."

At a two-hour, White House meeting yesterday with members of the House Appropriations Committee, Reagan strongly defended his SDI program.

The session was called to give the president and his top aides a chance to present their opposition to a proposed further reduction in funding of the SDI for the current fiscal year. The administration originally had sought $3.7 billion for fiscal 1986; that has been cut to $2.7 billion in the authorization bill and to $2.5 billion by the House Appropriations defense subcommittee.

An amendment to cut the money down to $2.1 billion is expected to be introduced Thursday.

In his presentation, Reagan said he would not trade limitations on SDI research for deep cuts in strategic nuclear weapons, according to several members who were present.

"We are not going to give it up or trade it away for reductions," one congressman quoted Reagan as saying.

The president also repeated an earlier threat -- made and then withdrawn by a White House spokesman -- that if the funding were cut, he may have to expand the SDI testing program beyond the current restricted levels, one participant said.