Defense Secretary Caspar W. Weinberger and Secretary of State George P. Shultz are expected to clash today at a closed National Security Council meeting called to discuss ways to handle expiration of the SALT II arms control agreement at the end of this year, according to informed sources.

Weinberger will argue that President Reagan should announce next week that at the end of the year the United States will abandon its promise to abide by provisions of the unratified treaty, sources said.

The defense secretary, who has gained Reagan's blessing in past arms control disputes with Shultz, will contend that the administration's policy of respecting the treaty as long as the Soviet Union shows restraint has been, in the words of one official, "totally unsuccessful" in getting Moscow to comply with the provisions of the treaty.

This source said Weinberger wants the president to begin preparing the country and the world for the expiration of the pact on Dec. 31.

Weinberger also will argue, one source said, that "Soviet forces will essentially be the same over the next five years with or without the treaty limits . . . as will ours."

The defense secretary also is expected to say that loss of the verification provisions in the SALT II agreement, which prohibit camouflage of missiles and coding test data, will have a minimal effect on the United States "since the Soviets are doing everything now as a practical matter to defeat" U.S. intelligence gathering.

Shultz, however, another source said, "will argue there is no need to make a decision now" and that announcing it will only add to Washington's problems with its West European allies over Reagan's "Star Wars" research program, or the Strategic Defense Initiative.

Shultz is expected to stress that the current policy gives the president flexibility to exceed some treaty limits if necessary.

Today's White House meeting is aimed at settling interagency differences before the president sends a report to Congress June 10 on his policies toward the SALT pact and other arms control agreements.

The president is not expected to make any decision today. Instead, sources said, Shultz will take soundings with NATO foreign ministers in Lisbon on Wednesday and Thursday, and a presidential decision will come by the weekend.

Weinberger also appears to have won the first skirmish on the SALT II issue. The Pentagon view has apparently prevailed on what to do when a new Trident submarine, the U.S.S. Alaska, goes on sea trials in August carrying 24 intercontinental missiles, placing the United States 14 missiles over a SALT II limit of 1,200 for such weapons.

The United States will remove from service, but not destroy, an older Poseidon submarine with 16 launching tubes.

State Department officials initially objected to that "gray area" approach, but sources said yesterday the Pentagon approach has apparently prevailed.

The Pentagon is expected to invoke military and political arguments in support of letting the SALT II limitations expire, sources said. The most controversial will probably be that the expiration will make little difference in Soviet missile production and deployment.

A Pentagon official said the Soviets have "embarked on a plan and the difference without SALT II will be trivial."

"Adhering or not adhering will have very little military consequence," this official said, noting as an example that if the Soviets increase the number of warheads on their biggest SS18 ICBM above the 10 permitted by the treaty, it would not have a big impact because many Pentagon intelligence analysts think it already illegally carries 14.

However, nongovernmental arms control organizations, the Congressional Research Service and even some Pentagon consultants have done studies that indicate Soviet warhead levels will increase faster without the treaty.

Even the Arms Control and Disarmament Agency's annual arms control impact statement found that without the SALT II limits, "the number of Soviet ballistic warheads could increase to at least twice their current levels with only a modest increase in the number of ballistic missile boosters."

On the already controversial subject of U.S. verification of Soviet compliance, a Pentagon official said, "Encryption of missile test data and camouflage are being carried out on a growing scale."