A strike threatened for 7 a.m. today was averted last night when negotiators for the Group Health Association and the union representing its 64 registered nurses agrreed to extend the nurses' current contract 24 hours as talks continued.

Both sides also agreed not to issue any further statements to the press unless a settlement is reached or negotiations break off.

Before the imposition of the news blackout, Thomas Gagligrdo, attorney for the nurses, and Dr. Edward J. Hinman, executive director of the 110,000-member health maintenance organization, both said that significant progress had been made during the day yesterday on most major noneconomic issues separating the two sides.

Shortly before 7 p.m. the nurses presented management with a revised economic proposal that Hinman said he expected to be "close enough (to management's last offer) so we'll get it done tonight."

"They have made significant modification of some of their demands and we have made significant modification of some of ours," said Hinman.

"At this point both sides are making a very positive effort," said Gagliardo, who represented Group Health's unionized physicians when they struck the organization for 11 days last spring.

While neither side would comment last night on the agreements reached thus far, the major issues separating the two sides have been questions of staffing, hours of employment, wages and pensions.

Sources said the major stumbling block in the negotiations before yesterday had been GHA's insistence that it was bound by President Carter's voluntary 7 percent wage-price guidelines, and any economic package offered the nurses would have to fall within that limit.

The nurses contended that GHA's recent imposition of a 10 percent rate increase remove the question of wage and price controls from the negotiations.

Group Health provides health care to about 10 percent of the residents of Washington and about 3 percent of the residents of the metropolitan area.