The State Department says it's confident that the relationship between the United States and Mexico is "strong enough to weather" GOP nominee Donald Trump and his comments about Mexico, as well as his surprise trip to Mexico today.

"We believe that the relationship is strong enough to be able to weather comments that are made by candidates running for political office here in the United States, or, frankly candidates in elected office in Mexico and what they might say," State Department spokesman John Kirby told reporters on Wednesday. "Our relationship is strong enough to weather those kinds of things."

Trump is visiting Mexico at the invitation of the nation's president, before giving a speech on immigration in Arizona. State Department officials played no role in the trip, beyond facilitating some security logistics.

"There was no such request for that kind of support or briefings," Kirby said. "There was no recommendation by embassy personnel or the ambassador with respect to whether this visit should occur."

Kirby also declined to "entertain speculation about what the outcome of this visit would be," although he allowed that the State Department is "interested" in how it turns out.

"Our focus is on the relationship now," he said. "We're not going to get into any speculation or conjecture about what may be discussed or what the impact of what may be discussed will be going forward."