Conversations with legislative leaders around the country indicate a "strong probability" that by June or July the required 34 states will have called for a constitutional convention to mandate a balanced federal budget, the president of the National Conference of State Legislatures said today.

Democrat Jason Boe, president of the Oregon Senate, said Congress has "got its head in the sand" on the issue despite passage by 22 state legislatures of some type of call for a convention to prepare a balanced budget amendment.

Of Congress, Boe said, "It's time they haven't done a thing about it," not even to establish a repository for the state resolutions.

California Gov. Edmund G. (Jerry) Brown Jr. recently added momentum by endorsing the convention idea on a statewide television hookup, and Boe said Brown's office contacted his about it.

The national legislative organization has not taken a position on the balance-budget question, but Boe said his the opportunity to discuss it with legislative officers of virtually every state. He also is a member of the Balance the Budget Committee headed by Maryland Senate President James Clark.

Last weekend Boe participated in a training seassion for new legislative presiding officers in Dallars, and said many of the 30 presiding officers there were interested in the convention proposal.

Noting that 49 of the 50 state legislatures (all but Kentucky) meet this year, Boe said, "We have assured ourselves it will be introduced in all states where it hasn't passed and in state where the form of approval may be weak."

Boe said he believed Congress should pass legislation establishing requirements and procedures for a convention so that legal questions could be clarified by the courts in advance.

For instance, he said, he believes the convention could be limited to a single issue, but if the Supreme Court decided otherwise, "nobody in their right mind would call a constitutional convention."

Another issue is whether the calls of the various legislatures have to be in identical wording; the present 22 measures differ widely. Boe cited a 1973 American Bar Association study that said the resolutions did not have to be identical, but he said Congress might hold otherwise and that, too, might be taken to court.

Once the necessary 34 states properly call for a convention, Boe said, "Congress has to act" -- either providing for the convention or preparing its own balanced-budget amendment for submission to the states for ratification. He said he had "no particular feeling which way it ought to go."