The sanctions mark a significant change for the Trump administration, which has veered between pressuring Moscow and taking a more conciliatory approach aimed at securing peace in Ukraine.
The European Union has also announced a new raft of sanctions against Russia, targeting its shadow fleet of oil tankers and banning imports of liquefied natural gas.
A 43-year-old friend had jumped into the water to try and assist him, but both ended up in difficulty. A police helicopter winched them back to shore, but they were unresponsive and could not be revived.
The American National Trust for Historic Preservation has called for all works to be halted until plans go through "the legally required public review processes".
If energy prices surge or allied unity splinters, Trump could find himself on the ropes following his announcement of sanctions on Russia's two biggest oil firms.
Economics professor Michael Ben-Gad says he was branded a terrorist by masked protesters from a group calling itself City Action for Palestine, and has rejected demands for him to resign.
In a major policy shift, the US has imposed sanctions against Rosneft and Lukoil and dozens of subsidiaries due to "Russia's lack of serious commitment to a peace process to end the war in Ukraine".