Defense Secretary Lloyd Austin on Saturday presented President Biden with several options for ways the United States can respond should Russia invade Ukraine, NBC News reports.

Austin also briefed Biden on different ways to move U.S. troops in advance of an invasion, a defense official and senior administration official told NBC News. The pre-invasion options include having bomber flights over the region, ship visits in the Black Sea, and moving troops and equipment from other parts of Europe to countries that border Ukraine, including Romania and Poland. 

Gen. Tod Wolters, commander of U.S. European Command and supreme allied commander Europe, has spent the last several weeks preparing options, the officials said. Wolters has the authority to move troops in the area, and the senior administration official said U.S. troops and assets could be repositioned “in the coming days.” The latest intelligence shows Russian President Vladimir Putin is continuing to send troops to the border with Ukraine, NBC News reports, and the defense official said Putin is “getting stronger, literally by the day.” 

The U.S. military and NATO are starting a 12-day maritime exercise in the Mediterranean Sea on Monday. Pentagon Press Secretary John Kirby told reporters the exercise, Neptune Strike ’22, is “designed to demonstrate NATO’s ability to integrate the high-end maritime strike capabilities of an aircraft carrier strike group, to support the deterrence and defense of the alliance.”