The United States and NATO on Wednesday rejected Russia's demand to bar Ukraine from NATO and pushed for a diplomatic solution to a crisis triggered by Moscow’s military build-up near Kyiv’s borders.

U.S. Secretary of State Antony Blinken and NATO Secretary General Jens Stoltenberg held separate press conferences on their responses given earlier in the day to Russia's sweeping demands for security guarantees in eastern Europe and the former Soviet space.

While neither the U.S. nor NATO made their written responses to Russia’s demands public, Blinken and Stoltenberg said the documents rejected Moscow's demand for a pledge that Ukraine will never join the NATO alliance.

"We make clear that there are core principles that we are committed to uphold and defend, including Ukraine's sovereignty and territorial integrity, and the right of states to choose their own security arrangements and alliances," Blinken said.

Stoltenberg likewise reiterated the Western military bloc's "core principle" of open-door membership.

Blinken said that Washington had set out to Moscow a "serious diplomatic path" to resolve the confrontation and outlined areas for bilateral cooperation, such as arms control.

NATO's response likewise outlined a series of areas where cooperation was possible, including increased transparency, mutual briefings on military exercises and joint efforts to combat cyber threats, Stoltenberg said.

A political solution to the standoff is "still possible," but depends on whether Russia acts "in good faith," Stoltenberg said.

"We've shown before that it is possible [to make] agreements with Russia that are beneficial for both Russia and the allies. … But of course, while we are hoping for and working for a good solution, de-escalation, we are also prepared for the worst," the NATO leader said. 

The U.S. and NATO responses come a month after Russia made public a list of ambitious demands for security guarantees that sought to limit the Western military bloc’s role in Ukraine and the former Soviet space.

Russia denies it is planning to invade Ukraine, instead accusing the U.S. and NATO of provoking tensions. Western countries point to Moscow's massing of 100,000 troops near Kyiv's borders as evidence it is mounting a large-scale offensive.

On Wednesday, Blinken said the U.S. was "ready" for whatever decision Russia makes and that its responses made clear that Washington would levy severe economic punishments on Moscow if it were to attack Ukraine.

"The ball is in their court," he said.