WASHINGTON (AP) — 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.

While he is leading the packed Republican field in early polls, the billionaire businessman has 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.

The Trump campaign did not respond to questions about the pledge late Wednesday, although RNC Chairman Reince Priebus is set to meet privately with Trump on Thursday in New York City shortly before Trump addresses reporters. The meeting was confirmed by an RNC official who wasn't authorized to discuss the plan publicly and requested anonymity.

In recent days, Trump has hinted he would soon decide whether to rule out a third-party bid.

"We're going to make a decision very soon," he said Saturday in Nashville, "and I think a lot of people are going to be very happy."

Several candidates contacted late Wednesday confirmed that they would sign the pledge, among them Ohio Gov. John Kasich and former Florida Gov. Jeb Bush, although few doubted the intentions of the vast majority of the GOP's 17 presidential contenders.

The Republican National Committee's pledge asks candidates to promise to "endorse the 2016 Republican presidential nominee regardless of who it is."

Further, it asks them to pledge "that I will not seek to run as an independent or write-in candidate, nor will I seek or accept the nomination for president of any other party."

An RNC spokesman declined to comment.