<p>The United States should threaten to retaliate if Russia does not stop attacking U.S. assets in Syria, former national security adviser Zbigniew Brzezinski wrote in a <a href="http://www.ft.com/cms/s/0/c1ec2488-6aa8-11e5-8171-ba1968cf791a.html#ixzz3niOkuTIK">Financial Times</a> op-ed published Sunday, urging "strategic boldness," with American credibility in the Middle East and the region itself at stake.</p><p>Moscow's apparent decision to strike non-Islamic State targets and those of Syrian rebels backed by the Central Intelligence Agency "at best" reflects "Russian military incompetence," and worst, "evidence of a dangerous desire to highlight American political impotence," wrote Brzezinski, the national security adviser for former President Jimmy Carter and a strong supporter of current President Barack Obama.</p><p>And if Russia continues to pursue non-ISIL targets, the U.S.