"So sad and unfair," Trump tweeted late Tuesday. "This would have been a great and much needed Conservative voice for and of the People." The Trump administration has been strict on antitrust matters in other media deals.
Earlier this week, Trump raised the possibility of antitrust claims against Amazon in a series of tweets. Trump in March blocked chip company Broadcom's proposed acquisition of Qualcomm, and the Justice Department said earlier this month it planned to challenge telecom giant AT&T's merger with Time Warner.
Trump-appointed FCC Chairman Ajit Pai said last week he had "serious concerns" about the proposed $3.9 billion acquisition and called for a hearing before an administrative judge.
Sinclair share prices gained 2.4 percent in early trading Wednesday. Shares of Tribune Media were up 1 percent.