WASHINTGON (BLOOMBERG) - Secretary of State Rex Tillerson signalled growing US impatience with China on issues from North Korea to trade while vowing to stay on the job as long as President Donald Trump will have him.

During a 30-minute interview at the State Department, Tillerson also showed increasing pessimism about the chance for a quick resolution to a standoff between Qatar and a bloc of nations led by Saudi Arabia. And he said the "pretty thick skin and thick armour" he developed as CEO of Exxon Mobil Corp. helped him shrug off rumours about tensions with Trump and reports that he's considered resigning over differences with the president.

"I'm motivated to serve the country and serve this president, and until somebody tells me your services are no longer needed or wanted, that's what I'm going to keep doing," Tillerson, 65, said.

About two weeks before Trump heads to Asia, the top US diplomat projected a tougher demeanour, particularly toward China whose help the US has sought to rein in North Korea's nuclear programme.

"I think it is important that China knows - OK, we've been having these conversations now for about six months," Tillerson said in the interview Thursday (Oct 19) in the State Department chamber where he receives visiting foreign diplomats. "We're expecting to see some change, we're expecting to see some movement, whether it's North Korea, or whether it's South China Sea, or whether it's trade." The remarks follow a speech he gave Wednesday in which he accused China of undermining the "international, rules-based order" and called it out for "provocative actions in the South China Sea." He visited China earlier this month and is likely to accompany Trump on his trip, which will include a stop in Beijing.

Tillerson made clear that the comments delivered in Wednesday's speech - where he also criticised Chinese financing that he said leaves developing countries saddled with debt - weren't off-the-cuff. They came as Chinese leaders were meeting in Beijing for a once-every-five-years Communist Party Congress outlining the government's strategy on the world stage.

"There was nothing in that speech yesterday that we haven't had a thorough exchange with our Chinese counterparts in these private dialogues," Tillerson said. "At some point there comes a time when it's appropriate to go ahead and start sharing with the rest of the world that we've talked about this." Tillerson spoke about China on a day when Central Intelligence Agency Director Mike Pompeo said the country has made progress in helping curb the nuclear threats from Kim Jong Un's regime in North Korea. Pompeo said the US is hoping it will do more given the "great relationship" that's developed between Trump and President Xi Jinping.

"There's been real progress there,'' Pompeo said at a conference in Washington. "Frankly, when I came into my new role in January of this year, if you had told the intelligence community that we could have expected the Chinese to do all the things that they have to date, there would have been great scepticism inside of our building, and there certainly would've been great scepticism around the world."

That mix of cooperation and pressure are part of a delicate balance that the administration must maintain as the US seeks China's help in cutting off North Korea's economy. Tillerson has said China can do more to coerce North Korea into giving up its nuclear-weapons programme.

Responding earlier Thursday to Tillerson's speech, Chinese Foreign Ministry spokesman Lu Kang called on the US to "abandon its biased views of China and make concerted efforts with China to focus on cooperation." Tillerson and Trump have sent conflicting public messages about US policy on global hot spots, including North Korea - Trump tweeted that Tillerson was "wasting his time" by pursuing negotiations - and Tillerson also appeared to criticise the president's response to the deadly protest in Charlottesville, Virginia, in August.

The secretary of state said in the interview he has little hope that the Saudi Arabia-led bloc's standoff with Qatar will end anytime soon, blaming the four countries lined up against the emirate for a lack of progress and casting doubts on US efforts to mediate the crisis.

Tillerson commented a day before embarking Friday on another round of diplomacy in the Middle East, including stops in Saudi Arabia and Qatar, in a renewed push to resolve the dispute. The crisis flared in June when Saudi Arabia and three other US allies in the region - the United Arab Emirates, Egypt and Bahrain - severed diplomatic and transport links with the gas-rich state over accusations that it supports terrorist groups. Qatari officials deny the charges.

"There seems to be a real unwillingness on the part of some of the parties to want to engage," Tillerson said. "It's up to the leadership of the quartet when they want to engage with Qatar because Qatar has been very clear: They're ready to engage." Tillerson declined to say which country bears the most responsibility for the lack of progress in the dispute, and made clear the crisis between U.S. allies is interfering with Washington's priorities in the region - from the Syrian civil war to the flow of refugees to Iraq.

"We have no intention of altering that relationship with any of them, but we do believe that this disagreement going on between them is unhelpful to their own interests and it's unhelpful to the regional objectives that we all have said we are aligned to pursuing," Tillerson said.