The D.C. zoning commission moved nearer to implementation of the Foreign Missions Act this week but delayed action on a key provision that would allow expansion of chanceries--embassy office buildings--located in low-density residential neighborhoods.

The act, passed by Congress last year, became law last Oct. 1, but cannot be used in the city until D.C. officials amend zoning regulations. A number of amendments, on which city and State Department officials have agreed, were forwarded to the National Capital Planning Commission for review, the next-to-last step before final approval.

The zoning commission last week passed emergency legislation--including the amendments sent to the NCPC this week and another that cleared the way for foreign governments to proceed with plans for expansion or moving in residential neighborhoods--subject to disapproval by the city Board of Zoning Adjustment. At least three--Japan, Portugal and Saudi Arabia--had appealed for action to enable them to move or enlarge chanceries.

Under the emergency measure, which will remain in effect for 120 days, any foreign government can expand its facilities in residential areas. James Wood of the State Department Foreign Missions office said he believes that, in addition to the three foreign nations already moving forward with plans, "two or three governments" may apply for some kind of property permits.

But commission members this week voted unanimously not to include this provision among amendments proposed for final approval.

Steven Sher, executive director of the city zoning commission, said he expects the NCPC to complete its review and return the approved amendments to the city in time for consideration on May 16.

The Foreign Missions Act requires foreign governments to get permission from the State Department to buy, sell, rent or expand property in the United States. The United States can use this requirement as leverage in demanding better treatment of American diplomats abroad.

The city has been reluctant to move swiftly with changes that would allow new or expanded foreign-government facilities in low-density neighborhoods where they are now prohibited. State, on the other hand, wants the act fully implemented as soon as possible.