The Washington Star plans to have 30,000 copies of its newly announced "A.M. Extra" edition on the streets by 6:30 a.m. when the weekday special goes on sale for the first time July 9, Star officials said yesterday.

Star Publisher George W. Hoyt said the newspaper plans to install hundreds of additional vending boxes in the Washington area to distribute the new edition. The Star is currently sold at about 4,500 newsstands, vending boxes and other outlets, he said.

Although the initial 30,000 A.M. Extras represent only a small increase over the 370,000 copies of The Star now printed on an average weekday, Star officials described the new morning street-sale edition yesterday as a significant boost for the afternoon newspaper.

"It's really just part of the continuing program to rebuild the newspaper," Hoyt said in a telephone interview. "The Star is on its way back."

The Star, which was acquired by Time Inc. in March 1978, has incurred multimillion-dollar deficits in recent years and said it expects to lose $16 million during 1979. Hoyt has predicted, however, that The Star will turn a profit within the next five years.

In starting an early morning edition, The Star will follow a pattern set by afternoon newspapers in Detroit, Dallas, Philadelphia and other cities. The Star said it plans to continue publishing its four other weekday editions. The earliest of these, the Capital Special, is now at newsstands by 10 a.m. The star already publishes morning editions on Saturdays and Sundays.

The Star's move to distribute an early morning weekday edition had been widely expected for some time. It was a subject of negotiations during an intensive round of labor-mananagement bargaining last winter. Key union contracts were modified to permit publication and distribution of morning editions.

Hoyt said the initial plan to print 30,000 early copies would be subject to revision after the Star's management determined how many copies were being purchased at vending boxes, newsstands and other outlets.

Hoyt left open the possibility that The Star might eventually consider providing delivery of the early morning edition to subscribers' homes. "We'll see what the demand and the market is," he said.

Such a move would put The Star in direct weekday competition with The Washington Post, and has been described by some newspaper analysts as a risky venture that could lead to steep financial losses for The Star.

The Star's average weekday circulation for the six-month period ending March 31 was 340,150 copies, according to the most recent publishers' statements filed with the Audit Bureau of Circulation. The Post's average weekday circulation was 598,213 copies for the same period.

The Star prints about 27 percent of the advertising published by Washington's two daily papers, compared with about 72 percent for The Post, according to ad linage data compiled by The Post.

John Morton, a newspaper analyst for the stock brokerage firm of John Muir & Co., described The Star's announcement of the A.M. Extra edition yesterday as "a smart move" that could help bolster The Star's circulation and advertising revenue eventually.

"Probably they're not going to make any money on this (immediately). But it's a psychological success - wanting to show that The Star is on an upswing rather than a downswing," Morton said. "It's an investment in their future, and to the extent that they get some new circulation out of it, it's a big threat to The Washington Post."

Post Publisher Donald E. Graham said, "It means more competition in the newspaper field - which is good. And The Post will do the very best it can do to put the best paper on the streets and in the hands of our customers."

According to Hoyt, The Star's A.M. Extra edition will go to press at 3:30 a.m., allowing the newspaper a competitive advantage over The Post. The Post's final edition, which is distributed at news stands and other vending outlets, normally goes to press at 2:30 a.m. Asked whether The Post might print its final edition at a later hour, Graham said, "We'll think about that."

Leaders of several key labor unions representing Star employes expressed cautious support yesterday for the planned A. M. Extra edition. They noted that it could provide additional jobs, but said it may also cause rescheduling of work shifts, a move they described as a possible problem. Hoyt said he expects the A. M. Extra to create about 50 additional full-time and part-time circulation, pressroom and other jobs.

In its announcement yesterday, The Star noted that the A. M. Extra follows other recent changes at the newspaper, including its acquisition last month of the right to start publishing "Doonesbury" and two other cartoon strips carried by The Post.