U.S. President Donald Trump says he "would not be happy" if North Korea conducts another nuclear test, which would be its sixth.
"I can tell you also, I don't believe that the president of China, who is a very respected man, will be happy either," Trump said of Chinese President Xi Jinping in an interview that aired Sunday on the CBS television network's "Face the Nation" show.
WATCH: President Trump on China and North Korea
Asked if "not happy" with another Pyongyang nuclear test meant he would undertake "military action" against the regime of North Korean leader Kim Jong Un, Trump said, "I don't know. I mean, we'll see."
North Korea, which is trying to develop a long-range missile capable of hitting the U.S. mainland 9,000 kilometers away, conducted a new missile test Saturday, but South Korea said it once again failed.
Trump, in a Twitter comment, said the test "disrespected the wishes of China & its highly respected President.... Bad!" But in the CBS interview, Trump said North Korea eventually "will have a better delivery system."
The U.S. leader described Kim Jong Un as "obviously ... a pretty smart cookie," but said the U.S. cannot allow North Korea to develop a nuclear weapon, and blamed prior American presidential administrations for not dealing with the Pyongyang's military ambitions.
Saturday's North Korean missile test came just hours after U.S. Secretary of State Rex Tillerson warned the United Nations Security Council of "catastrophic consequences" if the international community, and especially China does not pressure North Korea into ending its nuclear weapons development program.
The United States and South Korea on Sunday completed their annual large-scale military drills, which involved 20,000 South Korean troops and 10,000 U.S. forces. But the two countries continued their joint naval exercise in the Sea of Japan that Pyongyang has condemned as a provocation in preparation for an attack on North Korea.
The naval exercises included a U.S. aircraft carrier, the USS Carl Vinson, Trump dispatched to the region as a warning to North Korea. Through state media, North Korea has threatened to attack the battleship.
Trump, a real estate mogul turned Republican politician, also assailed opposition Democratic lawmakers in Congress as he started the second hundred days in his four-year term in the White House.
"The Democrats have been totally obstructionist," Trump told CBS, and said Senate Minority Leader Charles Schumer "has turned out to be a bad leader. He's a bad leader for the country."
On his Twitter account, Trump added, "They are only interested in themselves and not in what's best for U.S."
Asked what he had learned during his first 100 days as president, Trump renewed his frequent attacks on the mainstream U.S. news media. "One of the things that I've learned is how dishonest the media is, really," he said.
But he also complained about the pace of action in official Washington.
"It's just a very, very bureaucratic system," he said. "I think the rules in Congress and in particular the rules in the Senate are unbelievably archaic and slow-moving," where most major pieces of legislation require a 60-vote supermajority in the 100-member chamber.
He attacked continuing investigations in Congress and the Federal Bureau of Investigation about Russian meddling in the presidential election aimed at boosting his chances of winning.
"The concept of Russia with respect to us is total phony story," Trump said. "We have to find out what happened. I'd love to find out what happened. I can tell you one thing. Had nothing to do with us," referring to links between Trump campaign aides and Russian officials.
During his first 100 days, Trump failed in his effort to repeal and replace the national health care reforms that his predecessor, former President Barack Obama, considered to be his signature legislative achievement.
But Trump has been pressuring the Republican-controlled House of Representatives to vote on a revised measure to replace the law popularly known as Obamacare after Republican leaders withdrew repeal legislation in March when they did not have enough votes to pass it.
Trump tweeted, "You can't compare anything to ObamaCare because ObamaCare is dead. Dems want billions to go to Insurance Companies to bail out donors....New healthcare plan is on its way. Will have much lower premiums & deductibles while at the same time taking care of pre-existing conditions!"
Republican leaders say they will only hold a vote on a revised measure to repeal the seven-year-old Obama-era law if they believe they have enough votes to pass the legislation, even as national polls show Obamacare gaining in popularity.