Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) announced yesterday agreement between the administration and House Democratic leaders on three changes designed to move the stalled election-day voter registration bill through Congress.

House Majority Leader Jim Wright (D-Tex.) predicted the bill would now pass, but House Administration Committee Chairman Frank Thompson Jr. (D-N.J), whose committee reported out the bill some time ago, said it still would not be scheduled until just before or just after the August recess.

A committee source said the delay is designed to ensure that there are enough votes to pass the bill and to avoid having members use it as a vehicle for venting any lingering resentment over cuts in water projects and possible vetoes of appropriations bills now moving through the House.

The bill, which would allow voters to register to vote up to and including election day, is first in priority in a package of election bills proposed by the Carter administration.

Other items in the package include a bill to allow public financing of congressional campaigns, approved by a Senate committee yesterday, a bill to change the Hatch Act to allow participation in politics by now-restricted federal workers, passed by the House and awaiting action in the Senate; and a bill to change the electoral college which appears to have fallen by the wayside at least for this year.

The agreed-upon amendment to the Voter registration bill were announced after a breakfast meeting on the Hill between Vice President Mondale, handling the bill for the administration, O'Neill and other House leaders.