The Pentagon has balked at helping Congress cut the defense budget, throwing the legislative process into turmoil once again, a Republican Senate leader complained yesterday.

Sen. Ted Stevens (D-Alaska), assistant majority leader and chairman of the Senate Appropriations subcommittee on defense, said that, because of the Pentagon's balkiness, he had suspended voting sessions on the fiscal 1983 defense appropriations bill. Stevens said the Pentagon has rejected a list of cuts proposed by the subcommittee to keep the bill within the congressional budget resolution passed earlier this year. But the Pentagon, even though President Reagan has said he is willing to live within the congressional budget, has refused to come up with cuts of its own. "They are unwilling to give us alternatives," said an exasperated Stevens.

"I don't like to go out on the Senate floor with a bunch of amendments and have people fighting them because the Department of Defense doesn't support them," Stevens said. "I'm for a strong defense."

Stevens said he felt the administration had an obligation to help fashion cuts "once the president has agreed to a budget resolution."

Reagan created a stir over the summer when he said he would not be bound by the defense spending limits for future years--1984 and 1985--contained in the budget resolution. But he said he would abide by the 1983 figure, which many Republicans as well as Democrats had insisted upon to help hold down the deficit. For all three years the budget resolution proposed large increases for defense, but not as large as Reagan originally sought.

Stevens said he met with Defense Secretary Caspar W. Weinberger on Tuesday in a vain effort to obtain a list of 1983 cuts that the Pentagon would support. But Weinberger, who has been the most unbending of any Reagan's cabinet officers when it comes to defense cuts, did not offer any help, Stevens said.

Given this impasse, Stevens said he has decided to regroup. The Republican leader said staff members from congressional military committees, the Office of Management and Budget and the Pentagon will have to sit down again, as they did earlier this year, to work out a set of figures they can support for defense.

Stevens was unwilling to predict how long it would take to break this new impasse. A delay could work against the interest of the Pentagon because the so-called continuing resolutions that keep departments in business when they have no appropriations bills on the books usually limit them to year-before figures or one approved for the new year by the most relevant committee. Absent Senate action, that could turn out to be the House Appropriations Committee or its defense subcommittee, which are expected to vote for deeper cuts than the Reagan administration could endorse.

Stevens said yesterday that his subcommittee is only about half way to its objective of reducing the Pentagon's request enough to cut spending by $8.7 billion in fiscal 1983. Adding up the cuts already imposed in the bill authorizing money for weaponry, military construction and pay for service people, Stevens figured this would result in a spending reduction of $4.7 billion.

As a result of meetings yesterday Stevens said that the Pentagon and White House representatives tentatively agreed to accept $7 billion in cuts: $5.2 billion in programs, like major weapons, and $1.8 billion in pay.

"We're still $1.7 billion apart," said Stevens. He warned that unless agreement is reached on the rest of the reductions by Tuesday there will not be time to get a defense money bill to the floor before the October recess.