MOSCOW (AP) — The Russian ruble plunged 2.3 percent on Monday to hit a seven-month low amid a further drop in oil prices, the country's key export.

The ruble traded at 70.7 to the dollar in early trading in Moscow, its lowest level since Jan. 30, when Russian markets were hit by a combination of low energy prices and Western sanctions.

Oil is the backbone of the Russian economy and the fall of the ruble follows a sharp decline in the price of crude. The U.S. oil contract on Friday dropped below $40 per barrel for the first time since 2009 and on Monday was down another $1.23 a barrel at $39.22.

Russian officials have insisted that the economy is strong enough to weather the decline.

Speaking to reporters on Monday, Economic Development Minister Alexei Ulyukayev said he did not expect the price of oil to stay below $40 a barrel in the long term. The Russian government has budgeted all of its spending on an estimated oil price of $50 a barrel.