National Security Advisor Jake Sullivan has engaged in undisclosed talks with top Russian officials in recent months in hopes of reducing the risk that the ongoing war in Ukraine escalates into a nuclear conflict, according to a new Wall Street Journal report.

The newspaper cited U.S. and allied officials who confirmed that Sullivan held confidential conversations with Kremlin aide Yuri Ushakov and Russian Security Council secretary Nikolai Patrushev. It was unclear exactly on what dates and how many times Sullivan spoke with the officials.

The White House declined to comment on the report. Sullivan, meanwhile, traveled to Kyiv on Friday and pledged “unwavering and unflinching” U.S. support for Ukraine.

Amid a series of high-profile military setbacks in Ukraine in recent weeks, Russian president Vladimir Putin has repeatedly threatened to use his vast arsenal of nuclear weapons. In a speech in September announcing the mobilization of hundreds of thousands of troops to fight in Ukraine, Putin said Moscow was prepared to use nuclear weapons if Russia’s “territorial integrity” was threatened and “we will certainly use all the means at our disposal.”

Last month, international concern was again ramped up when Russia claimed that Ukraine could detonate a “dirty bomb” in an effort to frame Moscow—an allegation dismissed by both Ukraine and Western defense chiefs. Top diplomats of the United States, Great Britain, and France also issued a rare joint statement contending that the Kremlin could be using the false claim as a pretext to escalate its war on Ukraine.

Late last week, the International Atomic Energy Agency (IAEA) said that it had inspected three Ukrainian facilities and discovered no evidence of undeclared nuclear activity.

Meanwhile, in a pivot from Putin’s fiery comments, Russia’s Ministry of Foreign Affairs last Wednesday asserted that avoiding a nuclear clash is its top priority.  

The ministry said in a statement that it feared the world’s nuclear powers were teetering “on the brink of a direct armed conflict” and that the West needed to immediately stop “encouraging provocations with weapons of mass destruction, which can lead to catastrophic consequences.”

“We are strongly convinced that in the current complicated and turbulent situation, caused by irresponsible and impudent actions aimed at undermining our national security, the most immediate task is to avoid any military clash of nuclear powers,” the statement added, noting that a nuclear war “cannot be won and must never be fought.”

Ethen Kim Lieser is a Washington state-based Finance and Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek, and Arirang TV. Follow or contact him on LinkedIn.

Image: Reuters.