WASHINGTON (AP) — The Trump administration says it is not advocating regime change in North Korea after President Donald Trump tweeted that leader Kim Jong Un "won't be around much longer."

North Korea's top diplomat responded to that Monday at the U.N., telling reporters it was a declaration of war against his country by the United States, and that the North has the right to shoot down U.S. warplanes in international airspace.

A senior administration official said Monday that the U.S. policy is not regime change. The official was not authorized to comment publicly on the issue and requested anonymity.

The U.S.-North Korea war of words escalated last week. Trump warned North Korea of total destruction and the two leaders exchanged threats and insults.