It’s no secret that President Trump wants illegitimate Venezuelan dictator Nicolas Maduro out. But as the Trump administration pressures Maduro’s regime and continues to back opposition leader Juan Guaido, Russia has successfully positioned itself as a roadblock to Washington-backed regime change.

And if existing shadowy ties between the Moscow and Caracas weren’t already a serious concern for Washington, the two Russian air force planes that touched down in Caracas over the weekend certainly are.

Those planes carried 100 troops, a Russian defense official and almost 40 tons of cargo. They not only provide much-needed materiel assistance for Maduro, but they also send a clear message to Washington that the U.S. isn’t the only international player interested in Venezuela.

That Russia would take stronger steps to back Maduro isn’t entirely unexpected. Indeed, at the end of January there were already Moscow-linked military contractors on the ground in Venezuela to support Maduro. Moreover, Russia has been a staunch backer of Maduro’s regime, investing billions of dollars in military contracts and other projects. That has left Moscow with a vested interest in keeping Maduro in power, both to cash in on their monetary investments and to reap the rewards of their influence.

But the real motive for Russian President Vladimir Putin seems to be what Russian and before them Soviet leaders have always relished: challenging U.S. authority in what Washington views as its own backyard. Putin is complicating U.S. plans to end Maduro’s grip and restore stability to the region.

Russia's investment in the government of a failed state is likely to yield few if any long-term direct returns on investment. That makes this challenge to the U.S. the most plausible reason behind Moscow’s continued support for Maduro. Likewise, the 100 Russian troops that Moscow has put on the ground, even backed by a generous shipment of equipment, is hardly enough to secure an embattled regime, although it could be enough to create a headache for Washington.

Russia's actions not only make U.S. involvement more dangerous by introducing the potential to spark engagement with Russia, but they also undercut existing efforts against Maduro limiting the impact of sanction. They give Maduro new military power to rely on and lend him international backing even as the U.S. and other countries have increasingly isolated him.

Secretary of State Mike Pompeo warned on Monday that the U.S. does not take these actions lightly. As he put it, U.S. and its allies “will not stand idly by as Russia exacerbates tensions in Venezuela.”

Just what Pompeo has in mind is unclear. What is obvious, however, is that Russia has made Washington look weak.