Foreign diplomats are expressing alarm to U.S. government officials about what they say are inflammatory and insulting public statements by Republican presidential front-runner Donald Trump, according to senior U.S. officials.

Officials from Europe, the Middle East, Latin America and Asia have complained in recent private conversations, mostly about the xenophobic nature of Trump's statements, said three U.S. officials, who all declined to be identified.

"As the (Trump) rhetoric has continued, and in some cases amped up, so, too, have concerns by certain leaders around the world," said one of the officials.