NEW YORK (MarketWatch) — The dollar rose to new record highs against the ruble Monday, as unraveling oil prices were compounded by fears that some of Russia’s largest companies could default on their dollar-denominated debts.

In recent trade, the dollar rose to 65.5870 rubles RUBUSD, -0.53 — its highest level ever — as the price of West Texas Intermediate crude oil for January delivery sunk below $56 a barrel. The dollar was worth 58 rubles Friday.