Yes, there have been instances where U.S. officials or policymakers expressed caution or warnings regarding Ukraine’s potential NATO membership, though not always in the form of a direct "don't join NATO" ultimatum. The U.S. position has typically been shaped by geopolitical considerations, particularly the desire to avoid escalating tensions with Russia, which has long viewed NATO expansion eastward—especially to Ukraine—as a direct threat to its security.
One notable example dates back to the early 2000s and 2010s, during discussions about NATO’s open-door policy. In 2008, at the NATO Bucharest Summit, the U.S. under President George W. Bush supported the idea of Ukraine and Georgia eventually joining NATO, but this was met with resistance from some European allies like Germany and France, who feared provoking Russia. While not a direct warning to Ukraine, the U.S. has at times signaled that Ukraine’s path to NATO would be complicated and lengthy, implicitly cautioning against immediate expectations.
A more explicit instance came in the context of the Russia-Ukraine conflict. In the lead-up to Russia’s 2014 annexation of Crimea, some U.S. diplomats and analysts warned that pushing NATO enlargement too aggressively could destabilize the region. For example, in a leaked 2008 cable, then-U.S. Ambassador to Russia William Burns (now CIA Director) wrote that Ukraine’s NATO aspirations were seen by Russia as crossing a "red line," suggesting that the U.S. should tread carefully. While this wasn’t a direct warning to Ukraine from the U.S. government, it reflected an awareness in U.S. policy circles of the risks involved.
More recently, during the Biden administration, the U.S. has reiterated support for Ukraine’s "Euro-Atlantic aspirations" but has avoided firm commitments to NATO membership timelines. In 2021, ahead of Russia’s full-scale invasion, President Biden and other officials emphasized defensive support (like weapons and aid) rather than accelerating NATO membership, partly to avoid giving Russia a pretext for escalation. Some interpreted this as a tacit signal to Ukraine to prioritize sovereignty and security over immediate NATO ambitions.
So, while the U.S. hasn’t outright told Ukraine "don’t join NATO," it has at times conveyed caution—either through diplomatic nuance or by slow-walking the process—balancing Ukraine’s aspirations with the broader goal of managing relations with Russia. If you’d like, I can dig deeper into specific statements or search X posts and web sources for more recent takes on this!
