WASHINGTON — In a political embarrassment for Republicans, House GOP leaders on Friday abruptly canceled a vote on a bill to update the George W. Bush-era No Child Left Behind education law after struggling to find support from conservatives.

The bill would keep the annual testing requirements on schools but would give more freedom to states and districts to spend federal dollars and identify and fix failing schools. But conservative opponents said it doesn’t go far enough to let states and districts set education policy. Such conservative groups as Heritage Action for America and Club for Growth are among the opponents.

“We have a constitutional duty as members of Congress to return education decisions to parents and states,” Rep. Justin Amash, R-Mich., wrote this week on Facebook.

Democrats also dislike the bill and said it would abdicate the federal government’s responsibility to ensure that poor, minority, disabled and non-English-speaking students go to good schools and that billions of federal education dollars are spent wisely. The White House threatened to veto the bill, calling it “a significant step backwards.”

Senior Republican officials said it was unclear when a vote would occur. The officials spoke on condition of anonymity because they weren’t authorized to publicly discuss private negotiations.

“I look forward to continuing to discuss with my colleagues the conservative reforms in this legislation, and I expect we will have an opportunity to finish this important work soon,” Rep. John Kline, R-Minn., the sponsor of the bill, said in a statement.

Kline, chairman of the House Education and the Workforce Committee, said the delay happened because the debate over funding the Homeland Security Department had taken priority on the House floor.

The bipartisan 2002 No Child Left Behind law was a signature achievement of Bush, and its authors included the late Sen. Edward Kennedy, D-Mass., and current House Speaker John Boehner, R-Ohio.