Commodities pro Dennis Gartman says he knows how the White House can disarm the Russian economy's greatest weapon.
During an interview on CNBC's "Squawk Box" on Monday, the publisher of the Gartman Letter said the Obama administration should consider flooding the market with hundreds of millions of crude oil barrels from the U.S. strategic petroleum reserve, a move that could drive down crude prices $10 to $15 a barrel. That would severely damage the oil-rich Russian economy, Gartman said.
"The smartest thing they can do to counter what Mr. Putin is doing is to fight him on the one weapon he has, which is oil," Gartman said, adding that such a move would also boost the U.S. stock market.
His comments come as the U.S. and European Union allies weigh tougher economic sanctions against Russia, which continued to seize military bases from Ukraine in Crimea, storming a marine base Monday morning with stun grenades.
President Barack Obama meets with the world's developed powers at the G-7 summit this week in the Netherlands, where he plans to pitch stricter sanctions on Russia's economy as leaders discuss the heightened tensions between Russia and the West.
"You could send oil down sharply and do very real damage to the Russian economy," Gartman said.
(Read more: Gartman: This could send gold prices soaring)
A test sale of just 5 million barrels sent oil prices down $5 a few weeks ago, Gartman said. If the U.S. releases 275 million barrels from its strategic reserve into the market, the effect would be much greater, he added.
Russia is the third-largest producer of oil, behind Saudi Arabia and the United States, according to the U.S. Energy Information Administration. It's also the second-largest producer of natural gas, behind the United States. But Gartman said a trade war over oil would have deeper effects.
"The argument right now is we should be focusing on natural gas but that's years in the future," Gartman told CNBC. "I find that amusing."
(Read more: Europe 'held hostage' by Russian nat gas: Hamm)
—By CNBC's Jeff Morganteen. Follow him on Twitter at @jmorganteen.