WASHINGTON — Seeking to avert a 2016 disaster, the Republican National Committee on Wednesday challenged every GOP presidential candidate to sign a pledge not to undertake a third-party bid under any circumstances.

The challenge, confirmed by multiple campaigns, is aimed squarely at Donald Trump. And the timing of the pledge suggests an agreement has been reached.

While he is leading the packed Republican field in early polls, the billionaire businessman last month repeatedly threatened to launch a third-party bid — leaving open the possibility even at the GOP’s first presidential debate last month — should he fail to claim the Republican presidential nomination. Such a decision would make it all but impossible for the Republican Party to win the White House in 2016.

RNC officials have been working privately with Trump’s campaign for several weeks to avert such a scenario.

The Trump campaign did not respond to questions about the pledge late Wednesday.