Trump news: President U-turns on intelligence chief, as he announces A$AP Rocky has been released

China has responded by warning of retaliation for the new tariff, which it described as "blackmail".

Chinese Foreign Ministry spokeswoman Hua Chunying said: "If America does pass these tariffs then China will have to take the necessary countermeasures to protect the country's core and fundamental interests.

"We won't accept any maximum pressure, intimidation or blackmail. On the major issues of principle we won't give an inch."

She said that China hoped the US would "give up its illusions" about its strategy, adding: "We don't want to fight, but we aren't afraid to."

Mr Trump made the announcement on the new tariff despite warnings from his former top economic adviser that the trade war was damaging the US economy and actually helping China.

As the US formally withdraws from a 1987 missile pact with Russia today, an anonymous source in the Trump administration has told Reuters about plans to test new weapons "in coming weeks".

The Intermediate-range Nuclear Forces Treaty (INF) had blocked both countries from stationing short and intermediate-range, land-based missiles in Europe.

Mr Trump had announced the intention to withdraw from the treaty six months ago.

"As it has for many years, Russia chose to keep its non-compliant missile rather than going back into compliance with its treaty obligations," secretary of state Mike Pompeo said. "The United States will not remain party to a treaty that is deliberately violated by Russia."

Last month Vladimir Putin suspended Russia's participation in the treaty.

Meanwhile further missile tests have been carried out by North Korea, in what appears to be an attempt to pressure the US ahead of possible peace talks.

US official played down the launches on Friday, the third set in eight days. South Korea's government said the latest projectiles fired by the North appeared to be new short-range ballistic missiles.

They flew 220 km (135 miles) and reached an altitude of 25 km (15 miles), the Joint Chiefs of Staff (JCS) in Seoul said.

Mr Trump agreed to revive the talks during a meeting with North Korean leader Kim Jong Un on 30 June.

Mr Trump's announcement of further tariffs on Chinese goods - due to take effect on 1 September - have prompted stock market falls around the world.

In early trading, London's main index lost 2 per cent and Frankfurt fell 2.5 per cent. Markets in Tokyo, Hong Kong, Shanghai, Sydney and Paris also fell.

It comes after the Federal Reserve System cut its key interest rate for the first time in a decade Wednesday, citing uncertainty over the US trade conflicts. Mr Trump has called for even more aggressive rate cuts.

China's top diplomat has accused the US of "fanning the flames" of the Hong Kong protests, following meetings between Hong Kong opposition figures and US vice president Mike Pence, secretary of state Mike Pompeo and House speaker Nancy Pelosi.

"China expresses its strong indignation and firm opposition ... and demands they immediately cease interfering in Hong Kong affairs in any form," councilor Yang Jiechi told state media on Friday.

The US Embassy in Beijing responded: "We categorically reject the charge of foreign forces as being behind the protests.

"It is not credible to think millions of people are being manipulated to stand for a free and open society."

On Thursday Mr Trump had appeared to follow China's line on the Hong Kong protests, calling the demonstrators "rioters" and describing it as a matter "between Hong Kong and China."

Donald Trump has again threatened to release "thousands" of Isis fighters held in Syria unless European countries agree to take them back.

Other lowlights from the Trump rally in Ohio on Thursday night include a Don Quixote-style attack on "windmills".

After describing coal as "clean, beautiful", he launches into a routine about wind turbines, an important source of renewable "green" energy.

The previous administration, they liked windmills. You know windmills if a windmill is within two miles of your house, your house is practically worthless. They make noise they're intermittent, they kill your birds, they break down all the time. You have to replace them every 10 years because they wear out and they cost a fortune and they need subsidy - other than that they're quite good.

You don't want one of those windmills within vision. You hear them in noise. A lot of problems, no we're going to stay with the great energy that's powering our businesses, that's creating so many jobs.

And solar - you know what we'll live with solar, but solar is peanuts by comparison to what you need, but we're going to stay the way we have it. We've ended the war on American energy and we're putting our coal miners back to work and our steel workers back to work and our auto companies back to work.

That led on to some alternative history about the Soviet Union, which split into 15 states in 1991, and ended into an attack on the 2016 Paris climate agreement.

Remember the Soviet Union when it was all together the Soviet Union, when it was all together before they decided, we got to call ourselves Russia.

That was always their dream, to be the biggest in the world. Then it became Russia, and you know what they've done a good job with energy, and so has Saudi Arabia done a good job with energy, but we're now bigger than Russia. We are now bigger than Saudi Arabia by far and I withdrew our country from the job-killing, very expensive Paris climate accord.

Following the formal US withdrawal from the INF treaty with Russia,  NATO secretary-general Jens Stoltenberg told a news conference there would be "no rash moves" by the alliance.

"We don't want a new arms race," Mr Stoltenberg said.

NATO says "Russia bears sole responsibility" for the end of the treaty. "There are no new U.S. missiles, no new NATO missiles in Europe, but there are more and more new Russian missiles," said Mr Stoltenberg.