WASHINGTON — The chairman of the Republican National Committee has privately urged members of the party’s rules committee not to make changes to the guidelines governing the presidential nominating process, an effort to avoid the appearance that the party is seeking to block Donald J. Trump from becoming its nominee.

The chairman, Reince Priebus, whom associates describe as increasingly frustrated by Mr. Trump’s criticism of the delegate-selection process, sent a text message last week to multiple rules committee members strongly suggesting that they not alter the convention rules when the party convenes next week for its spring meeting in Florida, according to two who received the message.

Separately, a group of influential rules committee members held a conference call Thursday to prepare for the meeting and reached a consensus that they would derail any attempt at the gathering to make changes to the how the convention is conducted, according to a committee member on the call.