The United States plans to resume its funding of the International Atomic Energy Agency after having halted financial contributions last October when the agency voted to deny Israel its accreditation, a U.S. official said today.

Ambassador Richard T. Kennedy said that the agency's board of governors had taken action that satisfies a U.S. congressional amendment allowing U.S. funding only if Israel's right to participate in the agency is certified.

The United States thus is able to restore $8.5 millionin outstanding U.S. contributions and considerable additional money for technical assistance, and to resume participation in agency meetings. The IAEA is a specialized U.N. agency.

But Kennedy also told the meeting that the U.S. government would continue to observe the agency to see whether it allowed extraneous political problems to interfere with its work in promoting the peaceful uses of nuclear energy and guarding against diversion of atomic fuel for weapons.

Kennedy, who heads the U.S. delegation at the meeting of the agency's board of governors, declined to say specifically what the board had decided regarding Israel. He said that the meeting's deliberations were confidential.

But he said that the board had taken action "which will meet the provision of the U.S. law . . . and permit the resumption of U.S. financial contributions." The meeting will last until Friday.

A communique issued by the U.S. Embassy today also said that President Reagan has found the energy agency "critical to U.S. national security interests and our nonproliferation policy."

The conflict over Israel's membership rights broke out after Israeli forces destroyed a nuclear reactor in Iraq in June 1981. When the Israeli government refused to pay damages or put its own nuclear facilities under IAEA safeguards, 12 member states demanded the suspension of Israel from the agency. But the move was defeated when it failed to win a two-thirds majority.

The subsequent withdrawal of Israel's accreditation in the organization by a 41-39 vote, however, meant that Israel could no longer vote in the conference or be eligible for technical assistance. Although a number of western governments protested the measure, the United States was the only one to boycott the organization.

Kennedy said that the Reagan administration was seeking funds from Congress to continue its financial contributions to the agency, which up to now has received between 25 and 30 percent of its annual budget requirements from the United States.