Hamburg, Germany (CNN) President Donald Trump has long said China is the lynchpin to solving North Korea's saber rattling with missile tests. But his tact with the Asian superpower has run the gamut: He has thanked the Chinese for their support, argued they aren't helping defuse the situation and then written them off as willing partners -- all in the span of a few months.

On Saturday here in Germany for the G20, Trump urged action on North Korea as he met with Chinese President Xi Jinping.

"Something has to be done about it," Trump argued ominously during the brief public portion of his meeting with Xi.

There will "eventually be a success" against Pyongyang, Trump said. "It may be longer than I like, more than you like, but there will be a success ... one way or the other."

Trump's history with China -- particularly on North Korea -- will be brought to bear during the Xi meeting, their second sit down since Trump entered the White House in January.

Trump said at the start of the meeting that he and Xi had "developed a wonderful relationship."

The President also addressed trade issues before his meeting with Xi.

"Trade, as you know, is a very, very big issue for the United States now. Because over the years and -- it's really been over a long period of time many things have happened that have led to trade imbalances. And we're going to turn that around. And I know that with China in particular which is a great trading partner, we will be able to do something that will be equitable and reciprocal."

North Korea stance changing?

Secretary of State Rex Tillerson insisted in a briefing with reporters Friday that the Trump administration's "expectations are unchanged" on China's willingness to help address the growing problem in North Korea.

"We have not given up hope," Tillerson said. "I call it the peaceful pressure campaign. ... This is a campaign to lead us to a peaceful resolution because, if this fails, we don't have very many good options left."

That is not the case Trump made last month

"While I greatly appreciate the efforts of President Xi & China to help with North Korea, it has not worked out," he tweeted. "At least I know China tried!"

While I greatly appreciate the efforts of President Xi & China to help with North Korea, it has not worked out. At least I know China tried! — Donald J. Trump (@realDonaldTrump) June 20, 2017

Trump echoed that sentiment earlier this month when he tweeted, "Trade between China and North Korea grew almost 40% in the first quarter. So much for China working with us - but we had to give it a try!"

Trade between China and North Korea grew almost 40% in the first quarter. So much for China working with us - but we had to give it a try! — Donald J. Trump (@realDonaldTrump) July 5, 2017

The President even suggested earlier this year that he was holding fire on China -- by not labeling them a currency manipulator -- because of their work on North Korea.

"Why would I call China a currency manipulator when they are working with us on the North Korean problem," he wrote. "We will see what happens!"

The United States and China are currently split on the best way to deal with North Korean leader Kim Jong Un, whose recent test of what was believed to be an intercontinental ballistic missile -- a significant step for the North Korean regime -- has sent shock waves around Asia, Europe and the United States.

In response to the missile test, the United States and South Korea announced they held their own missile test to counter "North Korea's destabilizing and unlawful actions."

That response ran counter to what China and Russia had hoped the United States would do. In a joint statement, the two countries called on North Korea to stop nuclear tests and asked the United States and South Korea to stop future joint military drills.

"Our experience with China has been... a bit uneven," Tillerson said Friday. "China has taken significant action, and then ... they've paused and didn't take additional action."

He added, "We've remained very closely engaged with China, both through our dialogues that have occurred face-to-face, but also on the telephone. We speak very frequently with them about the situation in North Korea."

Trump told reporters in Poland on the first day of his foreign trip that North Korea was "behaving in a very, very dangerous manner" and warned Kim he had "some pretty severe things" available to him when asked about military action against North Korea.

Fighting China on trade, climate

Trump, when speaking to domestic audiences, has long cast China as an enemy of the United States, as he did throughout the 2016 campaign.

"I beat the people from China. I win against China. You can win against China if you're smart," he said at a campaign event in 2015. "But our people don't have a clue. We give state dinners to the heads of China. ... They're ripping us left and right. Just take them to McDonald's and go back to the negotiating table."

He later said in 2016 that China was "ripping us off" and that he was "so happy they're upset" that he is slamming them on trade.

Trump has also slammed the international power on climate policy, as well. When the President announced his intention to leave the Paris climate accord earlier this year, he targeted China as a primary reason behind the decision.

"China will be allowed to build hundreds of additional coal plants. So, we can't build the plants, but they can, according to this agreement," he said, adding later that the deal "is less about the climate and more about other countries gaining a financial advantage" over the United States.

China announced after the United States departures that it intends to stay in the agreement and work with European countries.