President Joe Biden was “crystal clear” on the consequences Russia will face should Moscow decide to invade Ukraine, National Security Adviser Jake Sullivan said in a press briefing following a two-hour-long video call between Biden and Russian President Vladimir Putin on Tuesday.

“[Biden] told President Putin directly that if Russia further invades Ukraine, the United States and our European allies would respond with strong economic measures,” said Sullivan. “We would provide additional defensive material to the Ukrainians above and beyond that which we are already provided. And we would fortify our NATO allies on the eastern flank with additional capabilities in response to such an escalation.”

The virtual summit came just days after an explosive intelligence analysis, first reported by The Washington Post, revealed that Moscow could be planning to launch a 175,000-troop offensive against Ukraine early next year. Leading up to the talk, Putin had warned Biden against crossing his “red lines” when it comes to Ukraine, seeking a guarantee that NATO forces would neither expand into Eastern Europe nor allow Ukraine to join as a member.

Biden’s response to that? “I don’t accept anybody’s red lines.”

According to Sullivan, Russia will have to deal with more than just sanctions in the case of a further offensive against Ukraine, and Washington isn’t ruling out the possibility of deploying more U.S. troops to help protect Baltic allies in case of a Russian invasion of Ukraine.

“They will be seeking, we expect, additional capabilities and potentially additional deployments, and the United States will be looking to respond positively to those things in the event that there is a further incursion into Ukraine,” said Sullivan, who later added that Biden made “no commitments or concessions” to Russian demands to block Ukraine from joining NATO.

Biden’s response to Putin’s “red lines” this week had earned him the ire of state television pundits and Putin loyalists across Russia. “Let him try to cross them... The Armed Forces of the Russian Federation remain in a state of military readiness and are ready to carry out any orders of our commander-in-chief,” Andrei Kartapolov, State Duma Committee on Defense leader, had said, adding, “Don’t play with fire. Don’t mess with us.”

Speaking to The Daily Beast on Monday, Ukrainian Defense Minister Oleksiy Reznikov said that the “the West did not react in time,” to recent Russian aggression. In the interview, Reznikov seemed pessimistic about the likelihood of Moscow keeping any diplomatic promises on Ukraine, and asserted that the only way to keep Russia at bay would be for NATO to help bolster Ukraine’s military.

“The [only] guarantee would be the West’s practical steps towards strengthening Ukraine’s defense capability and our army,” Reznikov said. “So that the price of a possible escalation would become unacceptable for the Kremlin’s military plans, and also, a clear preventive signal to Russia that the escalation of the war would destroy Russia economically. Only such an approach would be a guarantee.”