David Jackson

USA TODAY

WASHINGTON — A day after his secretary of State suggested the United States could act pre-emptively against North Korea if necessary, President Trump upped the ante with a tweet.

"North Korea is behaving very badly," Trump tweeted Friday. "They have been 'playing' the United States for years. China has done little to help!"

Trump and aides have long protested North Korea's nuclear development, including the prospect of missiles that could reach the United States and frequent threats against U.S. ally South Korea.

The United States has also called on China to rein in its neighboring communist regime.

During a tour of Asia this week, Secretary of State Rex Tillerson declined to rule out the possible use of force, saying all options are on the table.

"Obviously if North Korea takes actions that threaten South Korean forces or our own forces that would be met with (an) appropriate response," Tillerson said during a stop in Seoul. "If they elevate the threat of their weapons program to a level that we believe requires action that option is on the table."

Tillerson also said he hopes sanctions and other tools would help block the North Koreans.

Read more:

The first 100 days of the Trump presidency