WASHINGTON — President Donald Trump has been handing out his cellphone number to world leaders and urging them to call him directly, an unusual invitation that breaks diplomatic protocol and is raising concerns about the security and secrecy of the U.S. commander in chief’s communications.

Trump has urged leaders of Canada and Mexico to reach him on his cellphone, according to former and current U.S. officials. Of the two, only Canadian Prime Minister Justin Trudeau has taken advantage of the offer so far, the officials said.

Trump also exchanged numbers with French President Emmanuel Macron when the two spoke immediately following Macron’s victory earlier this month, according to a French official, who would not comment on whether Macron intended to use the line.

All the officials demanded anonymity because they were not authorized to reveal the conversations. Neither the White House nor Trudeau’s office responded to requests for comment.

The notion of world leaders calling each other up via cellphone may seem unremarkable in the modern, mobile world. But in the diplomatic arena, where leader-to-leader calls are highly orchestrated affairs, it is another notable breach of protocol for a president who has expressed distrust of official channels. The formalities and discipline of diplomacy have been a rough fit for Trump — who, before taking office, was long easily accessible by cellphone and viewed himself as freewheeling, impulsive dealmaker.