Americans in large numbers want the U.S. to reduce its role in world affairs even as a showdown with Russia over Ukraine preoccupies Washington, a Wall Street Journal/NBC News poll finds.

In a marked change from past decades, nearly half of those surveyed want the U.S. to be less active on the global stage, with fewer than one-fifth calling for more active engagement—an anti-interventionist current that sweeps across party lines.

The findings come as the Obama administration said Tuesday that Russia continues to meddle in Ukraine in defiance of U.S. and European sanctions. Pro-Russian militants took over more government buildings in eastern Ukraine, while officials at the North Atlantic Treaty Organization said satellite imagery showed no sign that Russia had withdrawn tens of thousands of troops massed near the border. (Read five takeaways from the poll.)

The poll showed that approval of President Barack Obama's handling of foreign policy sank to the lowest level of his presidency, with 38% approving, at a time when his overall job performance drew better marks than in recent months.

Mr. Obama defended his diplomacy-first approach at a news conference Monday in the Philippines, the last stop on a four-nation tour through Asia. He said those who called for a more muscular policy hadn't learned the lessons of the U.S. decision to invade Iraq.