AS ONE OF THE PROUD fathers of Greater Washington's Metrorail system, Montgomery Country Executive James P. Gleason surely remembers the perils-of-Pauline history of the subway project through its early years - those many times when Rep. William H. Natcher, the important House chairman, would withhold funds for Metro in an attempt to force local approval for highways. Most supporters of the subway system looked upon this treatment as nothing short of blackmail.

But now comes - of all people - James Gleason, with his own version of the natcher treatment. He says he's withholding millions of dollars in both operating and construction money for the metro system until he wins a federal guarateee that a subway line will be built through Wheaton. So it's phooey and nyeah, nyeah - and never mind that this childish stand has been repudiated by the county council, or that it threatens the entire regional financial plan for the subway system.

Metro General Manager Theodore Lutz has stated that Metro will be out of operating money in two or three weeks if the Montgomery County funds aren't available. Understandably, some of the other local jurisdictions aren't coughing up their shares until Mr. Gleason does. Moreover, Metro officials already have had to delay by one week the awarding of a contract for construction of the King Street station in Alexandria.

Mr. Gleason knows full well what any delays in construction can mean for Metro - namely, higher costs. Mr. Gleason must be aware too, that he has also set the stage for a county constructional battle. Legally, the council appropriates funds, but Mr. Gleason's office spends them. If he should continue his holdout, Mr. Gleason says the council "would have to beat me in court" to get the money for Metro.

While we share Mr. Gleason's concern for good public transportation along the Wheaton-Glenmont route, it's time to cut the antics before the entire system is damaged. As council member Jane Ann Moore notes in a Letter to the Editor on this page today, there is good reason for citizens and the Department of Transportation to get solid financial information on the transporation options for his route.

To be sure, the response from Transportation Secretary Brook Adams so far has been anything but clear. In a letter to Metro on the subject, Mr. Adams wrote that "no truncation of the route is contemplated" as part of the study to be made. Yet elsewhere in the same letter, he says that - get this - "the decision on whether the B-Route is to be constructed, and its timing, will depend upon the success of WMATA [Metro] and its consultants in achieving a design for the route that can be completed at costs significantly lower than currently estimated and which can be financed within the framework of a long-term financing plan covering capital and operating costs of the system."

Well, Mr. Adams and other cabinet officials have been under pressures from the Office of Management and Budget and the White House itself to cut costs - and that's why the study of this route was ordered. Nevertheless, while awating the new analysis, the Secretary ought to produce a better explanation of the administration's position. And Mr. Gleason should stop the blackmail.