Energy investor T Boone Pickens has postponed a fundraiser event for Donald Trump which had been scheduled to take place at his ranch next month.
According to reports in the US, the decision was taken due to conflicting scheduling issues.
Last month, the investor backed Trump for the US presidency.
He said at the time that the businessman was the only candidate who would be able to push real change.
Oil boss Harold Hamm had also previously thrown his support behind Trump.
A spokesman for Pickens said he intends to reschedule, most likely after the Republican National Convention in July in Cleveland.
The event had been intended as a fundraiser for the Great America PAC, which has been helping to boost pro-Trump spending.