WASHINGTON, D.C., Feb. 16--Many of the 1400 students who came to Washington to plead for peace and an end to nuclear testing are tired, disappointed, and frustrated tonight.

A mass rally, which this evening packed almost all the demonstrators into a small Methodist church, may have helped to revive flagging spirits and determination. But an indifferent or hostile Congress, inclement weather, and a lack of agreement on basic principles have dimmed the hopes of Project Washington.

Exhausted pickets arriving here after all-night bus trips were plagued and hindered by several hours of wet snow during the day.

Both delegations to Congressmen and participants in the picket lines often seemed unable to define the actual objectives of the Turn Toward Peace. While trying to convince Senators and Representatives of their objectives, Project representatives often end up fighting among themselves.

A Washington church, which had agreed to serve as the site of a major peace rally tomorrow, has cancelled its agreement with the group. A Project official admitted last night that several large auditoriums in the city had also refused to rent their facilities. He ruefully observed that "peace is apparently not universally popular."

But despite these obstacles, the number of students pouring into Washington to support the quest for peace continues to swell every hour. Student leaders of the Project predicted tonight that up to 4000 students may demonstrate in a peace march and mammoth rally tomorrow afternoon. About 200 participants, including most of the leaders of Project Washington, are from Harvard and Radcliffe.

A massive picket line around the White House, scheduled for tomorrow morning, will probably be contested by the Metropolitan Washington Council of the Young Americans for Freedom. Fulton Lewis III, the group's leader, asserted: "We cannot in all conscience permit this 'surrender operation' to go unopposed."