* Dollar index snaps four-day losing streak
* ECB frets over euro strength, trade war risk (Updates market action, comments)
NEW YORK, April 12 (Reuters) - The dollar snapped a four-day losing streak against a basket of major currencies on Thursday, as worries about the threat of an imminent clash between Western powers and Russia in Syria lessened.
The dollar index, which measures the greenback against a basket of six other major currencies, was up 0.21 percent at 89.758 after falling about 1 percent over four straight days.
U.S. President Donald Trump, who warned on Wednesday of immediate military action in Syria in response to a suspected poison gas attack, assuaged some fears after amending the warning on Thursday, saying a military strike "could be very soon or not so soon at all."
Trump said he was holding meetings on Thursday on Syria and expected to make decisions "fairly soon."
The threat of imminent military action piled pressure on investors already rattled by a trade dispute between the United States and China.
"It's a reversal of the safe-haven trade that lifted the yen and the Swiss franc earlier in the week," said Karl Schamotta, director of global product and market strategy at Cambridge Global Payments in Toronto.
"The primary reason for that is the dialing down of rhetoric from President Trump," he said.
The dollar was up 0.48 percent against the Swiss franc and 0.4 percent higher against the Japanese yen. The Swiss and Japanese currencies are often sought in times of global tension partly because the countries have big current account surpluses.
Data on Thursday showed new applications for U.S. unemployment benefits fell last week, pointing to sustained labor market strength.
"It dovetails with what we saw in the Fed minutes yesterday, really suggesting that the Fed is on autopilot at this point toward quarterly rate hikes in the year ahead," said Schamotta.
The euro was down 0.3 percent at $1.2328 after minutes from the European Central Bank's meeting in March showed that policymakers expressed concern over the risk of a full-fledged trade war with the United States and fretted over the potentially harmful impact of the euro's strength..
Investors were also concerned about a downturn in Purchasing Managers' Indexes across the euro area, Schamotta said.
"It very much looks like the euro area is losing some of the momentum that was carrying the currency higher over the last year and a half," he said.
Euro zone businesses rounded off the first quarter of 2018 with their slowest growth in over a year, as new business took another hit from a stubbornly strong euro, a survey in March showed.
To be sure, some market participants view the slowdown as temporary.
"In recent weeks, we see pretty good signs of slowing in Europe and Asia. We think this is a soft patch not a sustained downturn. This might last a couple of months," said Alessio de Longis, portfolio manager for OppenheimerFunds' global multi-asset group, in New York.
With the euro weak, sterling rose to a nine-month high against the single currency. Against the dollar, the pound was up 0.35 percent at $1.4226.
Cryptocurrency prices increased, led by a surge in bitcoin to two-week highs, with people active in the market citing a squeeze on traders who have bet against prices, given a lack of obvious news to trigger the gains. (Additional reporting by Richard Leong Editing by Susan Thomas and Steve Orlofsky)