U.S. President Donald Trump has arrived in Beijing for his highly anticipated summit with Chinese leader Xi Jinping at a restless moment for a world worried about war, trade and artificial intelligenc

Trump has also explicitly stated that he will discuss future US arms sales to Taiwan with Xi during this week’s summit. This violates one of the so-called Six Assurances that the US has upheld towards Taiwan since the 1980s, and which were endorsed by the US Congress in 2016.

Since the United States’ founding, four sitting presidents have been assassinated and several others have survived attempted murders. From Donald Trump to Ronald Reagan to the Roosevelts and Andrew Jackson,

"Today" host Jenna Bush Hager interviewed former Presidents George W. Bush, Joe Biden, Barack Obama and Bill Clinton ahead of America250.

The former presidents shared a message for the American people ahead of the nation’s 250th anniversary in July.

Add Yahoo as a preferred source to see more of our stories on Google. SAM 26000 operated as Air Force One from 1962 to 1998, carrying eight US presidents. Lyndon Johnson was sworn in on board, and the plane transported John F. Kennedy's body from Texas.

Included was an 1863 portrait of Abraham Lincoln that sold for $139,200, as well as an 1862 photo of his assassin, John Wilkes Booth, which secured $107,950

Defense secretaries have previously traveled with presidents on overseas trips, to provide advice and represent the U.S. military.