Rex Tillerson has arrived in Beijing for his first face-to-face talks with Chinese leaders expected to focus on North Korea's nuclear programme.
He said US military action against North Korea is an "option on the table", and warned the country to end its missile and nuclear programmes.
"The policy of strategic patience has ended," Tillerson said during his joint press conference with his South Korean counterpart, Yun Byung-se, on Friday.
"Strategic patience" is the term given to the US policy under Barack Obama when the US ruled out engaging the North until it made a tangible commitment to denuclearisation, hoping that internal stresses would bring about change.
Tillerson held talks with Wang Yi, China's foreign minister, on Saturday.
Yi gave warning last week that North Korea and the US-South Korea duo were like "two accelerating trains" headed at each other, with neither side willing to give way.
"The question is: Are the two sides really ready for a head-on collision?" Wang said. "Our priority now is to flash the red light and apply the brakes on both trains."
Wang said North Korea could suspend its nuclear and missile activities in exchange for a halt in joint US-South Korea military drills, a proposal quickly dismissed by Nikki Haley, US ambassador to the UN, who said the US has to see "some sort of positive action" from North Korea before it can take leader Kim Jong-un seriously.
First Asia visit
Previously, Tillerson had said in Tokyo that 20 years of diplomatic and other efforts, including a period when the US provided North Korea with $1.35bn in assistance "to take a different pathway", had come to nothing.
The US has been pressing China to do more to rein in North Korea's nuclear and missile programmes, including imposing tougher sanctions on North Korea.
However, China has been angered by the deployment of a US missile defence system to the South.
China says the system's radar is a threat to its security.
Al Jazeera's Adrian Brown, reporting from Beijing, said the Chinese government was worried about American statements that the US might take some sort of pre-emptive military action against North Korea in a worst-case scenario.
"What they are concerned about is the missile defence system that is now been deployed to South Korea," he said.
"The worry is that in the near future, if the North fires another long-range missile, this system might be used to intercept that missile, and that could eventually lead to military action against North Korea."
North Korea has a long-standing ambition to become a nuclear power and conducted its first underground atomic test in 2006, in the teeth of global opposition.
The country has continued to defy the international community for years, even after two rounds of UN-backed sanctions. It has conducted two nuclear tests and a series of missile launches since the beginning of last year.
North Korea recently launched four more ballistic missiles and is working to develop nuclear-tipped missiles that can reach the US.
Source: Al Jazeera and news agencies