Trump told reporters that it would be disloyal for DeSantis to run for president in 2024.
Trump said he regretted endorsing DeSantis in 2018, noting his backing helped him win.
Speaking to a group of reporters aboard his plane Monday, Trump conceded that DeSantis was "probably" his biggest rival, and said he regretted endorsing him for governor in 2018.
"And in the process, we beat the left day after day, week after week, month after month, year after year."
Trump and DeSantis have roughly the same favorability among Iowans, according to a Des Moines Register/Mediacom Iowa Poll released Friday.