US President Joe Biden and his Russian counterpart Vladimir Putin on Thursday spoke on the phone for 50 minutes without yielding any major breakthroughs.

Iran Press/America: The US and Russian officials said Biden and Putin held a "serious and substantive" discussion.

A US official said that Biden, during the phone call conducted from his home in Wilmington, Delaware, laid out two paths for Putin as he continues to amass Russian troops on the border with Ukraine: one a diplomatic route toward de-escalation and one focused on deterrence using economic sanctions, enhanced US troop presence on NATO's eastern flank and increased assistance to Ukraine.

Which path is chosen "will depend on Russia's actions in the period ahead," the official said, saying there would be "serious costs and consequences" should Russia proceed with its regional aggression.

Putin's dire warning

Putin responded with a dire warning, a Kremlin aide said. He told Biden that introducing a new round of sanctions against Russia would amount to a "colossal mistake" that could lead to a complete breakdown of relations between the two countries.

"A lot of such mistakes have been made over the past 30 years," Russian presidential aide Yury Ushakov said, "and it is advisable not to make such mistakes again."

The Biden-Putin talks come roughly two weeks before Americans and Russian diplomats are scheduled to meet in Geneva to discuss the ongoing crisis. In the lead-up to those discussions, Russia publicly offered a list of security concerns and demands it wants to be addressed, including a commitment that Ukraine never be allowed to join the NATO and that military equipment from the alliance not be positioned in its former Soviet states.

The United States has prepared its own list of concerns, a senior US administration official told reporters on Wednesday but isn't planning to release it publicly. Instead, Biden's advisers believe it will be more fruitful to keep the negotiations private.

The direct US-Russia talks will be followed by broader meetings between NATO and Russia, along with a meeting of the Organization for Security and Cooperation in Europe, where a slate of topics are up for discussion.