BUENOS AIRES, Feb 13 (Reuters) - Argentine stocks rose on Wednesday in tandem with external markets, which reacted positively to favorable economic data on the U.S. economy.
The positive trend in Buenos Aires was attenuated, however, by losses in index heavyweight Tenaris (TENA.BA) ahead of the expiry of options.
Options are futures contracts that mature on the third Thursday of every even month and generally affect the behavior of the market's most important stocks, with portfolio adjustments to cover obligations.
The MerVal index .MERV of 42 leading stocks rose 0.45 percent to 2,043.43 points, rebounding from a 0.73 percent drop earlier in the session.
"The MerVal followed the external trend, with a smaller rise due to Tenaris's weight on the index," said Diego Zabaleta, a broker at Besfamiglie brokerage.
Tenaris's shares, which weigh 14.01 percent on the leading index, closed down 1.85 percent at 61 pesos in Buenos Aires.
Volume on the broad market totaled a modest $23.7 million, with 46 issues advancing, 26 retreating and 12 unchanged.
On the local debt market, Argentine sovereign bonds <AR/BONOS> closed stable on average.
The gainers were led by dollar-denominated Par bonds, which rose 1.1 percent. Losers were led by the dollar-denominated Bonar 2013 bonds, which ended down 0.8 percent.
The peso currency ARS=RASL firmed 0.24 percent to end at 3.1525/3.1550 per dollar in formal interbank trade, where the central bank normally intervenes.
In informal trade between foreign exchange houses, as measured by Reuters, the peso ARSB= weakened 0.24 percent to end at 3.1775/3.1800 per dollar. (Reporting by Walter Bianchi; Writing by Gaspard Sebag; Editing by Jonathan Oatis)