The value of the dollar's net long position rose to $18.04 billion in the week ended Nov. 29, the highest level since the week ended June 8, 2010. In the previous week, long dollar bets stood at $12.11 billion.

Speculators increased their bets against the euro to 104,302 contracts in the latest week, from 85,068 contracts a week earlier.

Worries that the debt crisis is threatening Europe's core economies such as France and Germany have weighed heavily, pushing the single currency to its lowest in more than seven weeks on Nov. 25.

Short positions in the Swiss franc jumped to 9,327 contracts, the highest since May 2007. Speculation has grown in recent weeks that the Swiss National Bank may take further efforts, such as increasing the floor on the euro/Swiss franc exchange rate, to weaken its currency.

Bets against the British pound rose to 46,660, the highest in a month, the data showed.

To be short a currency is to bet it will decline in value, while being long is a view its value will rise.

The Reuters calculation for the aggregate US dollar position is derived from net positions of International Monetary Market speculators in the yen, euro, British pound, Swiss franc, Canadian and Australian dollars.