President Reagan said today that he would like to see the United States and the Soviet Union reduce their arsenal of strategic nuclear missiles and warheads by more than 40 percent but emphasized he was not rejecting any prospective Soviet offer.

When Reagan landed in Knoxville this morning for a day of speeches about his tax-overhaul plan, he was asked about published reports that Soviet Foreign Minister Eduard Shevardnadze will propose a 40 percent cut in strategic missiles and warheads when he meets with Reagan on Friday in return for "significant" restraints on the president's Strategic Defense Initiative (SDI), commonly known as "Star Wars."

Reagan's initial reaction to the question was to say, "It would be a better idea if it was more than 40 percent ."

After White House aides told the president that his remark could be interpreted as a rejection of the Soviet proposal before he had even seen it, Reagan answered additional questions at the Knoxville airport late in the day before he returned to Washington.

The president said that his earlier answer may have been "misunderstood."

"First of all, we have received no proposal officially of a 40 percent cut as I was asked about, and, when I made a remark that I wish it were more . . . I was doing that in the context of the fact that both Mr. Soviet leader Mikhail Gorbachev and myself said that we would both like to see the missiles done away with entirely," Reagan said. "But I was not turning down any offer, we've received no offer -- either here or our negotiators in Geneva have received no proposals."

In his earlier comments, the president said of the reported 40 percent reduction proposal: "I'd like to see it on the table with the arms control people in Geneva" and that he would "forward it to Geneva" if Shevardnadze made such a proposal this week.

Reagan, in his remarks before leaving Knoxville, reiterated that his goal was "total elimination" of nuclear missiles and added, "But we are perfectly prepared to take whatever mutual reduction we can get with the idea of eventually getting there to zero."

The president declined to react to a proposal made today by Shevardnadze at the United Nations for a "Star Peace" instead of "Star Wars."

"I'll wait until we get together and I hear exactly what they are talking about," Reagan said.

Reagan appeared to display some irritation with what his advisers have referred to as a public relations initiative by the Soviets. Reagan said that U.S. negotiators in the Geneva arms talks had made specific proposals to reduce nuclear weapons and had received no specific counteroffers from the Soviets.

"There has been no negotiating position presented by the Soviets," Reagan said.

A White House official said Reagan decided to answer questions about proposed reductions in the nuclear arsenals of the superpowers -- even though it drew attention from the tax-revision theme he was trying to emphasize today -- to make clear that the United States was not turning down any Soviet offer in advance or without thorough examination of the proposal.