(Adds dollar, yen and yuan details)
By Kate Duguid
NEW YORK, May 10 (Reuters) - Speculators cut their net long bets on the U.S. dollar in the latest week, according to calculations by Reuters and Commodity Futures Trading Commission data released on Friday.
The value of the net long dollar position was $38.08 billion in the week ended May 7, down from $38.88 billion the prior week.
To be long a currency means traders believe it will rise in value, while being short points to a bearish bias. The speculative market has been long on the dollar since mid-June last year.
U.S. dollar positioning was derived from net contracts of International Monetary Market speculators in the yen, euro, British pound, Swiss franc, and Canadian and Australian dollars.
In a broader measure of dollar positioning that includes net contracts on the New Zealand dollar, Mexican peso, Brazilian real and Russian ruble, the U.S. dollar posted a net long position of $34.34 billion in the week to May 7, compared with $34.92 billion the previous week.
Speculators cut their bullish positions as the dollar index fell after U.S. President Donald Trump on May 5 said he would increase tariffs on up to $200 billion worth of imports from China - a policy which went into effect Friday. The ratcheting up of trade tensions also drove the offshore Chinese yuan to four-month lows.
In the latest week, speculators cut short bets on the Japanese yen for the first time since mid-February . The Japanese yen is a safe-haven currency and has benefited from increasing trade tensions between the United States and China.
(Reporting by Kate Duguid Editing by Susan Thomas and Marguerita Choy)