When you are president of the United States, your words matter. And President Trump's poor choice of words in relation to Iraq last Sunday are now a major problem for U.S. strategic interests in the Middle East.

The problem arose when Trump was asked by CBS News why he is retaining a U.S. military presence in Iraq. Referencing the U.S. base at al-Asad in Iraq's western Anbar province, Trump explained, "I want to be looking a little bit at Iran, because Iran is a real problem."

Now, don't get me wrong, countering Iran is a good rationale for keeping U.S. forces in Iraq. That U.S. presence acts as a deterrent against Iranian regional aggression, a means of monitoring Iranian activity across the Iraq-Syria border and consolidating Iraq's Sunni community against Iranian-led sectarianism.

Yet, nuance is a necessity when it comes to U.S. presidents talking about Iraqi political concerns. And by so openly suggesting that the U.S. intends to use this base to act against Iranian interests, Trump has given fodder to Iraqi nationalist populism. Yes, many of those Iraqi politicians now suggesting that the U.S. withdraw don't ultimately want that. But Trump's words are tying their political hands to the emotional current.

The consequences of Trump's gaffe are significant. As Ali Mamouri notes, Iraqi politicians of all stripes are now considering whether the U.S. should be asked to leave al-Asad. Iran is laughing here. After all, the hardliners are under great pressure from all sides. But one quick, off-the-cuff remark by the U.S. president has given them a dream gift: a natural Iraqi demand that America withdraw.

The looming tragedy here is compounded by the fact that up until now, Trump has successfully applied U.S. influence in Iraq. Supporting Iraqi interests reconcilable toward a better future, the U.S. had promoted moderate politicians such as current Prime Minister Adil Abdul-Mahdi. At the same time, erstwhile U.S. enemies have shown deep frustration with Iran.

All this is now at risk. The president must learn from his mistake here. As a first step he should clarify his remarks in consideration of Iraqi concern. But going forward, Trump should pay more attention to global complexities. American interests and the president's legacy depend on it.