As earthmovers yesterday prepared to turn a corner of the Parade Grounds into a temporary home for New York Mets minor leaguers, the project was hit with two lawsuits.

Both suits argue that Mayor Giuliani should submit to community review its plan to create a $6.5 million, 4,500-seat ballpark across from Prospect Park by June.

Borough President Howard Golden filed one suit. The other was filed by community residents allied with activists from the Association for Community Reform Now.

Giuliani, with the city's Economic Development Corp. in the lead, says the community has no right to review the plans because the ballpark will be temporary.

The city is planning a permanent home for the Mets farmhands in a 6,500-seat, $31 million ballpark in Coney Island slated to open by 2001.

Giuliani granted sole-source negotiating rights to the Mets for the Parade Grounds and Coney Island, as he did with the Yankees for a minor league ballpark near the St. George ferry terminal in Staten Island.

The Staten Island plan appears on track, despite City Council grumbling that the city wants to begin construction on the $43 million ballpark even before a final lease is signed with the Yankees.

The Mets also have yet to sign a final concession deal for the Parade Grounds or the Steeplechase site in Coney Island, both of which are city parkland.

The Coney Island plan already faces tough sledding. Community Board 3 voted against it last week in an attempt to force Giuliani to simultaneously build a long-sought amateur sports complex on the site.

Mets Vice President Dave Howard, trying to keep the plans on track, yesterday said the team was willing to promise in writing to vacate the Parade Grounds field no later than the end of 2001 even if the Coney Island ballpark is not completed.

"At this point, we don't have a fallback position," Howard said when asked where the Mets' farmhands could play next year if the Parade Grounds deal is delayed.

He said the team was open to discussing changes, including a plan to turn one field into a parking lot for night games, with community leaders.

The Mets this fall bought a Toronto Blue Jays farm team that played last year in Ontario, Canada. The plan is to move it to Brooklyn to begin play in June in the short-season, Class A New York- Penn League.

It will be a Blue Jays farm team next year because the Mets' affiliation with the Pittsfield, Mass., franchise in the league runs through 2000.

Howard said the Coney Island ballpark could open by June 2001 if ground is broken by March. He said the team does not object if the city builds the Sportsplex arena, as demanded by community leaders, on the same site, but he said the ballpark is further along in its planning and should be allowed to proceed first.

The lawsuits filed yesterday ask a judge to stop construction on the Parade Grounds, with a preliminary hearing on a request for a temporary restraining order slated for this morning.

The lawsuits argue that the mayor cannot avoid review by calling the changes to the Parade Grounds temporary. City Charter provisions define a "major concession" as one involving more than 30,000 square feet of parkland or parking for 250 cars. The city plans to include parking for 750 cars on a facility covering 74,000 square feet for the ballpark alone, the lawsuits charge.

Bruce Brodoff, a spokesman for the Economic Development Corp., said officials there had not seen copies of the suits and could not comment on them.

Giuliani and corporation officials have said they did not have to submit the plans for community review, which would entail preparing time-consuming environmental assessments, because it is only a temporary move that would leave behind vastly improved fields after the Mets move on.