Washington has imposed a number of economic sanctions on Russia in retaliation for that country's push into Ukraine.
Getting European allies to do the same has not always been easy, since many of those nations trade with Russia and fear getting hurt themselves.
But the Europeans are not the only ones balking: The Pentagon also buys Russian military hardware.
When U.S. military and intelligence satellites are shot into space, all the rocket engines that propel them are made by a state-owned enterprise in Russia. They're sold to a joint venture of Lockheed Martin and Boeing, which has an exclusive contract with the U.S. government to launch those satellites.
At a Senate hearing this week, Sen. John McCain, R-Ariz., called it an outrage that one U.S. firm has a monopoly on that business, and that it depends entirely on Russia for its booster engines.
"The motor made by the consortium is made in Russia," McCain said. "That Vladimir Putin is responsible for our rocket motors should be a reason why we should be looking desperately for competition, rather than narrowing it," McCain said.
Facing McCain at the witness table was Frank Kendall, the Pentagon's top official for arms purchases. Kendall said the U.S. simply does not have a rocket engine that compares with the one made by the Russians.
"I've never been entirely comfortable with that dependency, and we have looked at, in the budget process, options a couple of times to try to do something about that, to remove that dependency," Kendall said. "But it just hasn't been affordable. And we've accepted that risk, and now that risk seems to be becoming much more real at this time."
That's the dilemma for the Obama administration: The desire to punish Russia collides with its reliance on Russian technology for national security priorities. For now, a resolution of sorts has emerged. A federal judge has issued an injunction barring any new deals with Russia's rocket engine supplier.
The rocket engines are not the only deal with Russia being challenged. The Pentagon also has 20 Russian military helicopters on order for Afghanistan's air force.
"I find it absolutely abhorrent and incomprehensible that this nation is providing taxpayer dollars to a Russian export agency that not only provides arms to [President] Assad in Syria, but also is in turn bolstering the Russian aggression in Ukraine," said Sen. Richard Blumenthal, a Democrat representing Connecticut, home to United Technologies, a leading helicopter manufacturer.
Blumenthal asked Kendall if the planned purchases of Russian helicopters could be scotched. Kendall did not rule that out.
"If we were statutorily ordered to, or if there was an order in the chain of command that told us to stop, then we would stop," he said. "But we hope that that does not happen ... because we need those helicopters for the Afghan air force."
Blumenthal insisted that American-made helicopters are superior to those made by Russia. Maybe so, said Sen. Adam Smith, the top Democrat on the House Armed Services Committee. But they would not work for Afghanistan, he said.
"The reason that we buy Russian helicopters for the Afghans is those are the only helicopters that the Afghan pilots know how to fly," Smith. "Those are the only helicopters that they are equipped to maintain. If we take them away, we cannot simply replace them with American-made helicopters that they don't know how to fly. It's that simple."
But complex, too. Senate Armed Services Chairman Carl Levin, D-Mich., urged his colleagues not to make any hasty decisions about the Russian helicopters.
"It's important that we look at the entire picture," Levin said. "Sen. Blumenthal raises obviously an important point, but we've got to see why it is that the commanders feel that it's essential that they be delivered in terms of Afghan support."