Donald Trump has dropped out of the Conservative Political Action Conference (CPAC), opting instead to campaign in Kansas and Florida.
The CPAC organizers said they were “very disappointed”.
The Republican presidential frontrunner was scheduled to speak on March 5 at the gathering of conservative activists in Maryland.
Donald Trump’s fellow Republican presidential candidates are all expected to speak.
“Very disappointed Donald Trump has decided at the last minute to drop out of CPAC – his choice sends a clear message to conservatives,” CPAC tweeted.
The statement said Donald Trump looks forward to attending next year, “hopefully as president of the United States”.
The decision could further damage an already-strained relationship with the GOP establishment.
Donald Trump was attacked on March 3 by former Republican presidential candidate Mitt Romney, who remains a central figure within the party.
Mitt Romney called Donald Trump a “phony” and a “fraud” and said his controversial policies threatened to make the world less safe.
Later on March 3, Donald Trump came under attack from his nomination rivals at a Republican debate in Detroit. Marco Rubio and Ted Cruz criticized the New York businessman for changing his position on various issues.
Donald Trump admitted he had changed his stance on issues but argued that flexibility was a strength.
Republicans in four states – Kansas, Kentucky, Louisiana and Maine – go to the polls on March 5.
Donald Trump has already won 10 of the 15 states that have voted so far, with his promise to “make America great again”.