(New throughout, adds details on the contracts, analyst comments, table; adds byline) By Gertrude Chavez-Dreyfuss NEW YORK, April 21 (Reuters) - Net short positioning on the euro increased to its largest since mid-March, according to calculations by Reuters and Commodity Futures Trading Commission data released on Friday, as speculators braced for the outcome of French elections over the weekend.
The first round of France's presidential election kicks off on Sunday, with polls suggesting the race will likely come down to a second-round duel between independent centrist Emmanuel Macron and Marine Le Pen, head of the anti-European Union and anti-immigrant National Front.
Euro's net short contracts rose to 21,649 in the week ended April 18, from 18,956, data showed.
"Our base-case scenario for these elections is for a euro-friendly outcome, with the final race taking place between Macron and Le Pen," said Thomas Flury, a strategist at UBS' wealth management research in Switzerland.
"However, we note that the odds of a euro-unfriendly outcome have risen," he added. Flury believes, however, that the euro's downside against the dollar remains well-protected as it has been in recent quarters." Speculators, meanwhile, lifted bullish bets on the U.S. dollar for a second straight week.
The value of the dollar's net long position totaled $15.34 billion, up from $15.04 billion the previous week.
The dollar has held up against the yen this week in the face of weakening consumer spending, inflation and manufacturing data, although it struggled against European currencies.
"The general resilience of the dollar can be attributed to the complacency of investors who believe that the recent disappointments in U.S. data changes nothing about the outlook for U.S. monetary policy," said Kathy Lien, managing director of FX strategy at BK Asset Management in New York.
CFTC data also showed that sterling net short contracts fell to their lowest since early March.
Sterling has been well-supported this week after British Prime Minister Theresa May surprised markets by calling for an early parliamentary election in June.
Investors viewed the election as easing political uncertainty and making it more likely that Britain could maintain some kind of preferential access to the single European market.
The Reuters calculation for the aggregate U.S. dollar position is derived from net positions of International Monetary Market speculators in the yen, euro, British pound, Swiss franc and Canadian and Australian dollars.
Japanese Yen (Contracts of 12,500,000 yen) $3.513 billion April 18, 2017 Prior week week Long 45,761 43,316 Short 76,224 78,080 Net -30,463 -34,764 EURO (Contracts of 125,000 euros) $2.904 billion April 18, 2017 Prior week week Long 185,786 173,594 Short 207,435 192,550 Net -21,649 -18,956 POUND STERLING (Contracts of 62,500 pounds sterling) $7.982 billion April 18, 2017 Prior week week Long 48,348 31,871 Short 147,838 137,772 Net -99,490 -105,901 SWISS FRANC (Contracts of 125,000 Swiss francs) $1.732 billion April 18, 2017 Prior week week Long 10,830 13,107 Short 24,632 23,235 Net -13,802 -10,128 CANADIAN DOLLAR (Contracts of 100,000 Canadian dollars) $2.486 billion April 18, 2017 Prior week week Long 37,306 31,432 Short 70,558 63,766 Net -33,252 -32,334 AUSTRALIAN DOLLAR (Contracts of 100,000 Aussie dollars) $-3.271 billion April 18, 2017 Prior week week Long 70,392 76,747 Short 27,130 31,596 Net 43,262 45,151 MEXICAN PESO (Contracts of 500,000 pesos) $-0.383 billion April 18, 2017 Prior week week Long 97,027 86,813 Short 82,783 99,488 Net 14,244 -12,675 NEW ZEALAND DOLLAR (Contracts of 100,000 New Zealand dollars) $1.057 billion April 18, 2017 Prior week week Long 18,320 19,008 Short 33,326 34,161 Net -15,006 -15,153 (Reporting by Gertrude Chavez-Dreyfuss, Editing by G Crosse and David Gregorio)