The U.S. views Europe as a strategic region for the continent's vital waterways, which provide access to the strategic depth of Russia and China. The expansionist plans of Russia and China has been a factor in strengthening the European relations with Washington. A joint military commitment to pivotal issues was also confirmed by NATO. However, the disagreement between the U.S. and Europe over dealing with the Iranian nuclear file remains present. Some analysts suggest that it is a strategic dispute as there are several factors threatening the relations between the two sides of the Atlantic ocean including the dispute over defense budgets in NATO, the imposition of high tariffs on Europe by the U.S. administration, and France's call for a unified European army.