Opponents of the three underpasses scheduled to be built on Memorial Drive claimed last night that they had enlisted a group of prominent state figures to their cause.

"A number of important leaders have already assured us that they are behind us in our efforts to prevent the destruction of Memorial Drive. In due course, an announcement of their support will be made," one source said last night.

Opponents believe the underpasses which will be built beginning in February or March of 1965, at River St., Western Ave., and Bolyston St. are merely first steps to the widening of Memorial Drive from a two-lane highway to a four-lane expressway. They further contend that the underpasses--and the changes that will follow--will destroy the Charles riverbank as a useful and irreplaceable recreational area.

To demonstrate Cambridge's support of this position, anti-underpass leaders hope to attract as many people as possible to the Charles riverbank Sunday, June 21.

Organizing opposition to the underpasses is the Citizens Emergency Committee to Save Memorial Drive, which is sponsoring the Sunday demonstration. And behind the committee is the grand old man of public relations, 72-year-old Edward L. Bernays.

To rally opposition, Bernays has declared June 21 "National Recreational Day" and has written the governors of the 50 states, asking for their support of what he calls "Play Rights" and "Grass Rights." In addition, the committee has invited Mr. Joseph Prendergast executive director of the National Rec- reation Association to speak at a luncheon June 21.

Bernays's appeal to the nation's governors is but a small chapter in his year-long battle against the underpasses. At one point, he asked Secretary of the interior Stewart L. Udall to name Memorial Drive and the Charles riverbank a "national historic site."

Although Udall declared that he was powerless to do this, he tacity encouraged Bernays. The Secretary said in a letter: "You are certainly to be congratulated on your energetic efforts to alert your community, so that all who will be most affected can take a good look at what is about to happen."

On another occasion, Bernays brought architect Peter Blake, the author of God's Own Junkyard, to Cambridge to oppose the underpasses and explain the technical side of highway and city planning.

Bernays's efforts and the visible opposition of Cambridge citizens (at two separate state hearings affecting the underpasses, nearly 500 irate residents showed up at the State House) have rocketed the Memorial Drive controversy onto the front pages of the Boston papers and into the national press. Time magazine wrote about the debate in its "Modern Living" Section, and Life magazine gave its support to the anti-underpass campaign in an editorial decrying poor urban planning.

The University has also fought the underpasses. In February President Pusey and James R. Killian, Jr., chairman of the board of M.I.T., met privately with Gov. Peabody to discuss the Memorial Drive situation.

Foes of the underpasses, say that besides destroying a valuable recreation area, the underpasses do not even represent a rational solution to congestion that plagues Memorial Drive during rush hours.

The Cambridge City Planning Commission agrees, and last fall offered an alternate solution, costing approximately $100,000, against $6 million for the underpasses.

Underpass opponents also state that the construction of the Massachusetts Turnpike on a route roughly parallel to Memorial Drive should ease the Drive's traffic problem considerably, making construction of the underpasses now premature.

Despite nearly unanimous opposition from Cambridge (the City Council has repeatedly gone on record opposing present plans), several bills that would have delayed, or stopped completely, the construction of the underpasses were defeated in the Massachusetts House of Representatives. The Massachusetts Legislature originally instructed the Metropolitan District Commission (MDC) to build the underpasses in 1962, though few Cambridge citizens learned about the proposal until last fall.

The main pressure on the legislature to retain the plans for the underpasses is coming from two Democratic Cambridge representatives: State Sen. Francis X. McCann, the sponsor of the original underpass bill, and Rep. John Toomey, chair man of the powerful Ways and Means Committee in the House. McCann has charged that opponents of the underpasses are really trying to ruin him politically.

Although most serious debate has centered on the destruction of open green space, and on city and highway planning, opponents have used a catch phrase--"SAVE THE SYCAMORES"--to gain support.

The rallying cry refers to the sycamore trees lining the Drive, some of which would be destroyed by the Bolyston Street underpass.

Seizing upon the sycamore about, Harvard and Radcliffe students took up the battle for Memorial Drive in their own way this spring. Nearly a thousand of them paraded down to the riverside, and, in a gay, cheerful mood, blocked traffic for more than an hour by sitting and standing in the roadway. MDC police, in a move that many felt tended to further excite the students, used dogs to break up the demonstration.

After a year of verbal skirmishes and legislative battles, the anti-underpass forces look forward optimistically to the next legislative session, which begins in January. With the new support they say has been promised them, they predict success before actual construction is scheduled to begin in the spring