While thousands of motorists lined up at D.C. government vehicle registration centers late yesterday, Mayor Marion Barry granted a one-week extension of the deadline for 1983 license tags, to midnight this Thursday.

Barry said that the action was justified because the Department of Transportation delayed mailing out applications this year while it awaited final action by the City Council on emergency legislation to postpone the effective date of a no-fault insurance law.

The original no-fault law would have required motorists to provide proof that they had automobile liability insurance before they could renew their tags.

"Because motorists had a slightly shorter time to renew their tags this year than in other years, I have approved this extension," Barry said.

Robert O.D. Thompson, the city's assistant director for motor vehicle services, estimated that the owners of between 10,000 and 20,000 vehicles have yet to purchase new tags.

The original deadline for renewing auto tags was last Thursday at midnight.

Yesterday, officials reported a light turnout throughout the morning at the Municipal Center, 301 C Street NW, and at two satellite centers near the Carter Barron Amphitheatre in Northwest and the Fort Dupont Ice Arena in Southeast. By early afternoon, however, applicants were swarming the three centers.

No auto tag purchase centers will be open this weekend. Beginning Monday, the only location where new tags can be obtained will be the Municipal Center. It will be open from 8:15 a.m. to 4 p.m.