A national coalition to block a constitutional convention on a balanced federal budget will meet for the first time in Washington. D.C., on Friday to plan strategy for the late-starting campaign.

The bipartisan coalition, led by Massachusetts Lt. Gov. Thomas P. O'Neill III, has enlisted big guns from business, labor, academic and political circles to stop the snowballing convention drive, recently joined by California Gov. Edmund G. (Jerry) Brown Jr.

Favorable resolutions have already been adopted in 28 states. Six more states are needed for a constitutional convention to be called.

The coalition has attracted such names as Laurence Tribe, a constitutional law expert from Harvard, and Douglas Fraser, president of the United Auto Workers union.

O'Neill, the group's leader, is the son of the speaker of the U.S. House, Thomas P. (Tip) O'Neill Jr., who is also an ardent critic of the proposed constitutional conclave.

The younger O'Neill, who heads the Massachusets office of state-federal relations in Washington, said he has no "real disagreement" with the notion of a balanced federal budget. But he is wary of calling a convention that "would cause serious and far-reaching damage to our Constitution."

Tribe, who recently drafted a constitution for the Marshall Islands, saw "real peril" that a convention might be unable to limit itself to the issue of the federal budget, that it would be " a rogue elephant."

Convention proponents have called such charges "scare tactics."

At a legislative hearing on the issue here this week, Edward F. King, a former Republican gubernatorial candidate (not to be confused with incumbent Gov. Edward J. King), said, "The idea that a new constitutional convention could simply run wild is nonsense."

Added James Davidson. chairman of the National Taxpayers Union: "It is a false charge that this movement has been conducted under a blanket of secrecy."

O'Neill's aides said the strategy session at the Hyatt Regency in Washington is expected to include such groups as the American Civil Liberties Union, Common Cause, National Association for the Advancement of Colored People, League of Women Voters and Americans for Democratic Action.

This week the proposed constitutional convention was attacked on Capitol Hill. "I am both alarmed and frightened by the very prospect," said Sen. John Stennis (D-Miss.). Sen. Edmund S. Muskie (D-Maine.), chairman of the Senate Budget Committee, said the budget-balancing convention would trigger "a constitutional mess of enormous proportions."