In every meeting of NATO officials, there comes the inevitable conversations about burden sharing and the exchange of fiscal platitudes furnished by member states that continue to fall short of their financial obligations to the alliance. The U.S. representative, often Defense Secretary James Mattis but occasionally even the American president himself, will remind the organization that the United States foots the majority of the bill and provides the majority of the troops that NATO relies on as a deterrent force, and the 23 out of 28 full-fledged members that continue to fail to meet their obligations will mumble to one another about incremental increases and timetables. Thursday’s meeting of NATO officials, which will be attended by Mattis, will be no exception but this time, the U.S. will be asking for even more.

In the four years since Russia’s military annexation of Crimea, NATO has been working to shore up defenses along the continent’s eastern border. Although NATO’s total troop count far exceeds that of Russia’s standing military, officials tasked with defending that border have repeatedly pointed out that NATO’s forces are not close by, organized, or ready to counter a legitimate Russian incursion. At best, even NATO’s latest troop deployments throughout Europe hope to stall a Russian invasion long enough to mount an international counter-offensive — an endeavor many fear would take too long to be feasible under current NATO models.

It’s with that concern in mind that Mattis is expected to pressure America’s allies for more than just their club dues, he will also be pushing for an agreement among his counterparts to devote enough troops and resources to countering Russia’s aggression to stand up 30 land battalions, 30 air fighter squadrons and 30 navy ships ready to deploy to the region within 30 days of being put on alert. The total number of personnel this would entail could vary significantly, as the size of a battalion varies widely across NATO member states. One NATO battalion may include anywhere from 600 to 1,000 troops, which means the total endeavor may entail as few as 18,000 or as many as 30,000 troops, as well as air craft and support personnel the fighter squadrons and the varying requirements posed by naval vessels fielded by different national navies.

“We have an adversary (Russia) that can move quickly into the Baltics and Poland in a ground attack,” said one NATO diplomat who requested that his identity be withheld. “We don’t have the luxury of taking months to mobilize.”

In February, NATO announced plans to stand up two new commands, bringing the total number of active commands tasked with countering the Russian threat to nine, still far fewer than the 33 NATO maintained at the height of the Cold War. At the time, it was seen as a step in the right direction, but there was little doubt that even the two new command elements and associated personnel was not enough to serve as a legitimate deterrent.

While the intent behind this American-led initiative is obviously European defense, a number of variables could lead to an unfriendly reception to the proposal. Since Donald Trump’s election, there has been a growing sentiment throughout Europe that the continent needs to establish a military alliance more akin to the European Union than NATO — ending the continent’s reliance on the United States for defense and establishing a unified European military. There has been no talk of dissolving NATO in favor of this new force, but the EU has already begun laying the ground work for its establishment, and nations may soon have to decide between devoting troops and resources to one organization or the other.

“We only have a certain amount of forces in Europe, and they cannot be committed to every military proposal,” one NATO official was quoted as saying to Reuters.

The question of spending could also limit support for this endeavor, as it would undoubtedly require a significant investment from nations throughout the alliance — and spending is always a tricky subject when it comes to NATO.