China has taken "significant steps" to help solve the Korean Peninsula nuclear issue, a senior U.S. State Department official said on Wednesday.

In a conference call with reporters on U.S. Secretary of State Rex Tillerson's upcoming trip to southeast Asia, Susan Thornton, acting assistant secretary of state, said that the United States had seen "significant steps ... frankly, unprecedented steps" by China to increase pressure on the Democratic People's Republic of Korea (DPRK).

"We see a growing determination on their part to take steps to try to address the situation seriously," said Thornton.

"We and China have the same goal, which is denuclearization of the Korean Peninsula," she added.

It was the second time in two days that the leadership in the U.S. State Department had contradicted U.S. President Donald Trump's recent rant that China does "do NOTHING for us ... just talk" on the Korean Peninsula nuclear issue.

Speaking here at a briefing on Tuesday, Tillerson also said to achieve the goal of denuclearization on the Korean Peninsula, the United States seeks to "partner with China," and that the United States doesn't blame the Chinese for the situation on the Korean Peninsula.

Tillerson's remarks came days after the DPRK launched its second intercontinental ballistic missile (ICBM) in a month, following the first being launched on July 4.

The DPRK confirmed the Saturday's test-firing of the second ICBM was simulating its maximum range, which it said can cover all the territories of the United States.

China has always called for negotiated solutions to the nuclear issue on the Korean Peninsula.

Liu Jieyi, China's permanent representative to the United Nations (UN), said on Monday that China is firmly opposed to any violation of the UN Security Council (UNSC) resolutions, including nuclear tests and ballistic missile tests by the DPRK.

China has been urging the DPRK and other relevant countries not to exacerbate the situation on the Korean Peninsula by avoiding words and actions that could escalate regional tensions, which run counter to the objectives sought by the UNSC.

China has been working with Russia to put forth a road map for achieving regional peace and the UNSC's objectives, the Chinese ambassador told a press conference at the UN.