WASHINGTON (AP) - President Bush's overhaul of federal education laws may have to wait until September to see his signature, with Congress struggling to complete work on the president's top priority before lawmakers break for the summer.

House and Senate lawmakers on Thursday said they would work hard to reconcile differences in the two versions of the bill, but admitted that the job will be difficult with only three weeks remaining before their August break.

``We're going to give it all the time and the attention and the focus we can,'' said Sen. Edward Kennedy, D-Mass.

Kennedy said it was ``not out of the question'' that lawmakers would deliver the bill to Bush before the Aug. 3 recess, but several lawmakers said they face an uphill battle in doing so. The House, they said, won't even name members of the negotiating committee until next week.

``We're extremely sensitive to the White House's wishes to be done in August,'' said Sen. Judd Gregg, R-N.H. ``We will use our best effort to do so, but realize it may be difficult.''

The possible delay would mean little for most students as they begin school in the fall, since the money provided wouldn't be distributed until next July.

Last spring, the House and Senate separately passed similar versions of the Elementary and Secondary Education Act, which provides most of the federal funding for K-12 education. Negotiators must now work out a compromise between the two bills.

Both measures bring several major changes to the federal system, foremost among them the requirement that schools annually test students in math and reading in grades three through eight and once in high school. Students at schools in which scores don't improve could use federal money for tutoring or transportation to another public school.

All schools would get more flexibility in their use of federal funds, while under the Senate bill a small number of states and school districts could compete for a pilot program giving them even fewer restrictions.

In the House version, school districts could use up to half their federal money without supervision, with 100 school districts - two per state - eligible for a program that would free schools from virtually all spending restrictions.

The two versions also differ dramatically in how much money they would provide for public schools. The House version proposes about $24 billion, while the Senate version asks for $33 billion.