Billionaire real estate investor Tom Barrack, a friend of President Trump, is the front-runner to be named U.S. ambassador to Mexico, according to a report Wednesday.

A White House official told Politico the job will be offered to Barrack "if he wants it," but he has expressed some concerns about taking the job. It would be challenging for Barrack to sell his considerable assets, Politico said.

Barrack is a prominent Trump surrogate, having planned the president's inauguration.

According to The New York Times, Barrack helped introduce Trump to Paul Manafort, the former campaign manager being investigated for his ties to Russia.

The U.S. and Mexico have endured a tense relationship in the Trump administration as the president has implemented an aggressive immigration enforcement strategy and moved to renegotiate the North American Free Trade Agreement.