REUTERS, Wilmington

US President Joe Biden and Russian President Vladimir Putin have exchanged warnings over Ukraine but conveyed some optimism that diplomatic talks in January could ease spiraling tensions.

In a 50-minute call, their second conversation this month, Biden said he needed to see Russia decrease its military build-up near Ukraine, while Putin said sanctions threatened by Washington and allies could lead to a rupture in ties. The call was requested by Putin.

The leaders’ exchange set the stage for lower-level engagement between the countries, including a Jan 9-10 US-Russia security meeting, followed by a Russia-Nato session on Jan 12, and a broader conference including Moscow, Washington and other European countries slated for Jan 13.

In Kyiv, leaders worry about the 60,000 to 90,000 Russian troops that have gathered to its north, east and south. Russia denies planning to attack Ukraine and says it has the right to move its troops on its own soil.

Biden reiterated his threat of unprecedented sanctions if Russia chose to invade Ukraine.

Kremlin said Putin “immediately responded” that any sanctions now or later “could lead to a complete rapture in ties between our countries.” He added: “Our president also mentioned that it would be a mistake that our descendants would see as a huge error.”

The Kremlin said Biden appeared to agree with Putin’s contention that Moscow needed some security guarantees from the West and also that he said the US did not intend to deploy offensive weapons in Ukraine.