In a speech Monday in Ohio, Trump will argue that the United States needs to work with anyone who shares that mission, regardless of other ideological and strategic disagreements. Any country that wants to work with the U.S. to defeat "radical Islamic terrorism" will be a U.S. ally, he is expected to say.

"Mr. Trump's speech will explain that while we can't choose our friends, we must always recognize our enemies," Trump senior policy adviser Stephen Miller said Sunday.

On the eve of the speech, the Clinton campaign slammed Trump's campaign manager for ties to Russia and pro-Kremlin interests, an apparent reference to a New York Times story published Sunday night. The story alleges Paul Manafort received $12.7 million from Ukraine's former pro-Russia president and his political party for consultant work over a five-year period. The newspaper says Manafort's lawyer denied his client received any such payments.