NEW YORK (MarketWatch) -- The U.S. dollar briefly spiked against the ruble Thursday after Russian President Vladimir Putin vowed to punish currency speculators during his annual address to Parliament. Putin said the ruble was the target of a "speculative attack" and called for the central bank and the Russian government to implement harsh measures to prevent it from weakening further. The dollar USDRUB, +0.71% rose as high as 53.96 rubles after the speech before returning to 53.48, its level from Wednesday afternoon. The ruble has lost nearly 40% of its value against the dollar so far this year.