Defense Secretary Frank C. Carlucci dismissed as "pure propaganda" and "nonsense" a Soviet charge that the United States would undercut the new superpower nuclear arms treaty if NATO pursues plans to upgrade its arsenal of nuclear weapons permitted under the pact.

Carlucci's reponse to an attack on North Atlantic Treaty Organization plans last month by Soviet Foreign Minister Eduard Shevardnadze came as the Senate Foreign Relations Committee began its second week of hearings on the Intermediate-Range Nuclear Forces (INF) Treaty to eliminate medium- and shorter-range nuclear-tipped missiles.

Carlucci arrived at the hearing with green plastic models of U.S. missiles to defend the treaty against earlier criticism from Sen. Jesse Helms (R-N.C.) and wound up defending his record at the Central Intelligence Agency against new Helms charges concerning disputes over treaty verification.

Helms said the CIA failed to predict Soviet violations of the unratified SALT II treaty while Carlucci was deputy director of the agency, raising questions about Carlucci's assertions now that the INF Treaty is verifiable.

Carlucci defended the CIA's record in assessing Soviet capabilities and said the violations were detected when they occurred, denying Helms' charges that he had ever said the SALT II treaty was fully verifiable.

Their exchange came amid another acrimonious clash between Helms and committee Democrats over an earlier Helms charge that the Soviets are probably already cheating on the INF Treaty by hiding SS20 missiles that are to be destroyed under the pact.

Sen. Paul S. Sarbanes (D-Md.) accused Helms of misquoting from a newspaper article on Soviet buildup plans, and Helms responded by accusing Sarbanes of "nitpicking."

In testimony on the INF agreement, Carlucci said the treaty and its negotiating record spell out clearly that both sides can modernize weapons that fall outside the 300- to 3,400-mile range proscribed by the INF agreement, although he added that the treaty would probably prohibit any weapons modernization within that range.

"I think it's very important we go ahead" with the permitted weapons development, said Carlucci, who urged in a report to Congress last week that it lift restrictions on new nuclear missiles and artillery shells for deployment in Europe.

Shevardnadze warned during a recent visit to Bonn that plans under discussion by NATO to upgrade battlefield-range and other nuclear weapons permitted by the INF Treaty would "scuttle everything that has been achieved in the sphere of nuclear disarmament and . . . must not be permitted."

Carlucci also contended that failure to ratify the INF agreement would lead to expansion of Soviet nuclear weapons in Europe without assuring continued deployment of similar U.S. weapons.

While the Soviets would be likely to continue building up their European nuclear forces, including advanced new weapons, he said, Senate rejection of the INF Treaty would make it politically difficult for western European countries to reverse themselves again to allow U.S. missiles on their soil.

"It would be like fighting the deployment battle all over again," he said in reference to disputes over Pershing II missiles in Europe during the early 1980s.

Meanwhile, at the Senate Armed Services Committee's INF ratification hearing, former NATO commander Gen. Bernard Rogers criticized the treaty and said it would leave the alliance militarily weak.

Reviewing the treaty's history, he said the Pershing II and ground-launched cruise missiles were intended as measures to bolster NATO's military power, not as negotiating tools to oppose the Soviet SS20 missiles.

Rogers, who retired in 1987 after eight years as NATO's top military officer, said the treaty was opposed by a number of officials from NATO governments whom he declined to name.