Tiankai said in a Tuesday interview with Fox News that Washington repeatedly "changed its mind overnight" and sunk deals that could have ended the two countries' trade war.
The US and Chinese leaders are also set to meet again at the G20 summit in Japan next month.
The federal government will spend an additional $16 billion to help farmers hurt by the US-China trade war, Agriculture Secretary Sonny Perdue announced Thursday.
"Regarding the relevant U.S. measures, China has lodged solemn representations", Commerce Ministry spokesman Gao Feng said at a weekly briefing in Beijing.
President Trump, who once declared that trade wars were "good" and "easy to win", has embraced protectionism as part of his "America First" agenda.
After a six month ceasefire, trade talks between the two sides broke down earlier this month, prompting the USA decision to increase punitive duties on Chinese imports and Beijing's subsequent retaliation.
Chinese President Xi Jinping has said this week that his country must prepare for a long trade war with the United States, citing the Mao Zedong-led communists' long struggle for victory in the Chinese Civil War against the Kuomintang.
F-22s intercept Russian bombers, fighters off Alaska coast
The Russian planes were "positively identified", the agency wrote. All civilian craft entering the zone must identify themselves.
"The idea is not to have tariffs, the idea is for them (China) to treat our companies fairly", Mnuchin said on Wednesday, and referred to the impact on USA agriculture, which has been among the targets of China's retaliatory tariffs.
Trump a year ago already promised farmers a $12 billion aid package to help mitigate the first wave of Chinese retaliatory measures after Trump slapped tariffs on Chinese imports.
Of the nearly 250 respondents to the survey, which was conducted after China and the United States both raised tariffs on each other's imports earlier this month, nearly three-quarters said the impact of tariffs was hurting their competitiveness. Fitch further noted that the rising trade tensions between the United States and China are already creating a ripple effect across Asia, weakening demand across the supply chain and dampening business confidence in the first half of 2019.
He reiterated the security risk the Trump Administration says is posed by Huawei's technology and said he expects other global companies to elect not to use their products.
"China is open to the door of dialogue, but sincerity is indispensable to make a consultation meaningful", Lu said at regularly scheduled briefing.
He said Washington has "seriously affected the development and cooperation of global science and technology, and has also harmed the vital interests of relevant enterprises and countries".
Perdue acknowledged that United States farmers have been hit hard by the escalating trade fight with Beijing. The Trump administration has singled out Huawei, accusing it of posing a security threat.
His comments came as the American Chambers of Commerce (AmCham) in China and Shanghai released a survey of its members that found that slightly more than 40% had relocated, or were considering moving production facilities, outside of China because of tariffs.