Speculators' net short dollar bets rose in the latest week after seven straight weeks of declines, according to calculations by Reuters and Commodity Futures Trading Commission data released on Monday.

The value of the net short dollar positions, derived from net positions of International Monetary Market speculators in the yen, euro, British pound, Swiss franc and Canadian and Australian dollars, was $3.15 billion, in the week to Nov. 21.

That compares with a net short position of $643 million the previous week and marks the 19th straight week that speculators have had a net short position on the greenback.

To be short a currency means traders believe it will fall in value.

Meanwhile, the net short position in the Swiss franc grew to the largest since June 2012, the data showed. (Reporting by Saqib Iqbal Ahmed; Editing by Tom Brown)

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