The county attorney for Harris County said today the lease tying the Houston Astros and the Astrodome together appears to be breakable, although the price could be as high as $20 million.

The 40-year lease, signed in 1965 and revised slightly in 1982, requires the Astros' ownership to pay an annual rent of about $1 million per year through the year 2005, County Attorney Mike Driscoll said today.

But Driscoll said the lease says only that the Houston Sports Association, the Astros' owner, has "the right to" use the premises for baseball games. Driscoll said it apparently does not specifically require the Astros to play there, or even to remain in Houston.

As the primary owner of the Astros, John J. McMullen is also the major shareholder in the Houston Sports Association, which operates the Astros, the Astrodome and the adjoining facilities Astrohall and Astroarena. McMullen may be looking to Washington, D.C., as a relocation site for the 1987 season, several baseball sources have said.

McMullen has told Houston sources he lost about $10 million in the last two years on the team's baseball operations, but made about $6 million from the other facilities, which are sites for such events as rodeos and conventions.

McMullen appears to be upset that he is losing money while Harris County and the City of Houston are making money from the Astrodomain complex.

Houston sources say a University of Houston study found that the Astrodome and its complex bring about $500 million into the city's economy each year.

"No one seems to recognize that," McMullen told a Houston reporter. "We need assistance, and we need help from the community. All of us have worked hard, but one group cannot do it all."

If McMullen is serious about moving the Astros from Houston to Washington -- as sources say he is -- he could come up with the $20 million from the other Astrodome operations or ask Washington-area investors to pay the $20 million, according to Houston sources.

What McMullen would be paying is $745,000 annual rent, plus about $100,000 annually in service fees and $125,000 annually in parking fees. The $745,000 is the amount of rent necessary to amortize the bonds paid to build the stadium, a source said.

Houston sources also say there are other ways the lease could be broken, one being that McMullen could contend that Harris County has reneged on the deal.

One escape clause says that if the county "fails to exercise reasonable diligence to carry out, comply with or exercise any of its obligations," HSA can end it.

McMullen has said many times he wants 10,000 seats added to the 45,000-seat Astrodome and is angry that a $500 million bond package, which would include $53 million for Astrodome improvements and added seats, has not been sent to the voters.

Houston government officials have said the area's economy is so depressed that any such bond package would be defeated.

Regardless, if McMullen does intend to leave Houston, he will face the same kind of legal challenge as has confronted other owners who have moved, or sought to move, franchises.

"It raises the issue of public possession," Driscoll said. "If the Astros really represent such an important draw to the city, it might be worthwhile for a public entity to buy the Astros from McMullen."