The Carter administration yesterday officially revealed details of the new strategic arms agreements currently being negotiated with the Soviet Union, and assured the Senate that the United States will be able to verify Soviet compliance with them.

In an unusual communication to the Senate Foreign Relations Committee, the Arms Control and Disarmament Agency revealed that the United States and the Soviet Union have agreed to ban all mobile, land-based intercontinental missiles.

The ban - on deployment or testing of such weapons - would remain in force for the life of a protocol that had previously been described as lasting three years. However, yesterday's letter revealed that the protocol would expire in September, 1980 - which is likely to be barely two years after negotiations are completed, according to administration sources.

A senior U.S. diplomat involved in the strategic arms limitation talks (SALT) said yesterday that an agreement could not be concluded before this summer at the earliest.

A fornight ago the Soviet Union in a bitter published attack accused the United States of stalling the talks unjustifiably.

Yesterday's ACDA statement for the first time included official confirmation of details of the ongoing negotiations that have appeared repeatedly in leaked news accounts. It suggested that there has been no significant change in the bargaining situation for months - except perhaps on the issue of mobile missiles.

The United States is anxious to ban these missiles because it believes the Soviet Union would have substantial advantages in using them, for technological and geographical reasons. The United States has plans for a $40-billion-dollar mobile missile program known as MX, that would put mobile missile launchers in vast underground trenches, but the cost and complexity of the system makes it unattractive to administration planners.

It could not be learned last night if the agreement to ban mobile missiles is a recent one.

The decision to disclose publicly the number of weapons of different kinds that the two superpowers propose to allow each other under the new SALT agreements was made unilaterally by the administration, at the urging of several senators and staffers on the Foreign Relations Committee.

The ACDA statement released yesterday also included unclassified sections of a new analysis of the verifiability of the new SALT pacts, potentially a controversial issue when they are submitted for Senate approval.

The statement began with a general assurance that the agreements would be verifiable which goes far beyond previous public statements. Government sources said this new statement was approved by the relevant government offices, including the Joint Chiefs of Staff.

The statement acknowledges that the Soviets will be able to cheat on some aspects of the new agreements, but says "such cheating would not alter the strategic balance in view of U.S. programs." This appears to be a reference to U.S. ability to respond in kind quickly if cheating is discovered.

"There will be areas of uncertainty, but they are not such as to permit the Soviets to produce a significant unanticipated threat to U.S. interests and those uncertainties can, in any event, be compensated for with the flexibility inherent in our own program," the statement said.

This is likely to provoke heated dispute in the Senate. An aide to one senator who is skeptical of the proposed new agreements yesterday called the ACDA statement "wholly inadequate," and "not a serious piece of work."

"If this is the quality of work we can expect from the administration on SALT," this aide said, "we're in real difficulty."

The idea that the United States can afford to accept an arms pact which the Soviets can admittedly evade, even partially, is likely to be challenged in hearings on verification that will be held by Sen. Henry M. Jackson's (D-Wash.) arms control subcommittee of the Senate Armed Services Committee.