U.S. intelligence agencies and the Pentagon's Strategic Command are working on a new evaluation of whether the Russian and Chinese leadership could survive a nuclear strike and keep operating, even as President Donald Trump seeks to reshape relations with both nations.

The new study, ordered by Congress before Trump took office, drew bipartisan support from members who harbor deep concern about China's increasing military boldness and distrust of Russian President Vladimir Putin's intentions.

While Trump has pledged to "greatly strengthen and expand" U.S. nuclear capabilities, he also has predicted he can make deals with Putin that may include reducing U.S. sanctions in return for future cuts in nuclear arsenals. The two leaders talked by phone for about an hour on Saturday.