Any American attempt to pull off a 1985 Plaza Accord-type coordinated depreciation of the US dollar likely won't work as it would require the consent of China and Europe, Japan's former top currency diplomat Naoyuki Shinohara said on Tuesday.

Some analysts believe the Trump administration may push through a "Mar-a-Lago Accord" – a grand bargain to weaken the overvalued dollar – to reduce the huge US trade deficit.

Unlike for the Plaza Accord when the United States could work just with close allies Japan and Germany, Washington would need to engage more countries – including the China and European Union – to weaken the dollar effectively in a globalised market, Shinohara said.

Having antagonised China and Europe with his decision to impose what he describes as reciprocal tariffs, US President Donald Trump will find it extremely difficult to get their consent, Shinohara added.

"In times like now, you need China to be in the loop, as well as European nations," Shinohara said in an interview.

"That would be quite hard under the current circumstances.

"Currency intervention, even if coordinated among nations, has become less effective because markets have become so big."

As Japan's vice finance minister for international affairs from 2007 to 2009, Shinohara negotiated with his US and European counterparts for their cooperation in curbing sharp yen rises that were hurting Japan's export-heavy economy.

He was also deeply involved in world-wide efforts among policymakers to deal with the global financial crisis caused by the collapse of Lehman Brothers in 2008.

"In most past shocks, one could identify the cause," Shinohara said.

"For the current one driven by Trump, it's hard to tell when and how many times shocks could hit" due to the president's back-and-forth comments on tariffs.

"That's leaving investors unsure how to respond" and keeping markets volatile, he said. (Reuters)