* Dollar falls for fourth day, worst run since March
* Greenback weakness boosts EM FX and commodities
* Graphic: World FX rates in 2017 tmsnrt.rs/2egbfVh
* For a live blog on European stocks, type LIVE/ in an Eikon news window (Adds detail, updates prices.)
By Alasdair Pal
LONDON, Aug 21 (Reuters) - Critical comments by U.S. President Donald Trump about the country's central bank saw the dollar fall for the fourth straight day in its worst spell since March, boosting emerging market stocks and currencies in the process.
In an exclusive interview with Reuters, Trump said late on Monday he was "not thrilled" with the Federal Reserve under his own appointee, Chairman Jerome Powell, for raising interest rates, and said the Fed should do more to help him to boost the economy.
American presidents have rarely criticized the Fed in recent decades because its independence has been seen as important for economic stability.
"The Fed is independent in setting monetary policy and markets were spooked by yet another comment from Donald Trump criticising higher interest rates," said Artjom Hatsaturjants, an analyst at Accendo Markets.
The dollar index, which tracks performance against a basket of six major currencies, fell 0.39 percent on Tuesday.
It has now fallen 1.2 percent in the last four days, its worst such run since late March.
The dollar's weakness took pressure off many emerging markets, which have struggled in recent weeks as worries over Turkey precipitated a sell-off across the globe.
MSCI's benchmark emerging equities index rose 1 percent and was set for a third day of gains after Trump's comments.
Chinese mainland shares jumped 1.8 percent, South Korea 1 percent and Indonesia 0.9 percent. In Europe, Turkish stocks rose 1.6 percent and Polish shares 0.8 percent.
The Chinese yuan rose by 0.17 percent to 6.8427 per dollar. The currency was on track for its fourth session of gains, pulling further away from 6.934, its weakest since January 2017 marked last week.
The yuan had weakened to a 19-month low against the dollar earlier this month amid concerns over the country's economic growth, a Sino-U.S. trade war and a broad rally by the dollar.
In his Reuters interview, Trump also accused China of manipulating its currency and said there was little hope of progress in the ongoing trade dispute between the two countries in talks due this week.
Other emerging-market currencies, including the South African rand, Thai baht, Mexican peso, Hungarian forint and Polish zloty were all higher by 0.2 to 0.9 percent against the dollar.
Commodities that are priced in dollars and so benefit from any weakness were also higher across the board.
Base metals prices rose, with London copper climbing for a second day and crossing the $6,000-a-tonne mark. Spot gold rose 0.28 percent to $1,193 .
Brent crude oil rose 0.33 percent to $72.45 per barrel.
In developed market equities, defensive sectors were in favour, with areas considered less dependent on the economic cycle like healthcare, utilities and consumer staples among the leading gainers in Europe.
Futures in the United States pointed to the blue-chip S&P 500 index opening 0.2 percent higher.
Reporting by Alasdair Pal; editing by Louise Heavens, Larry King