Donald Trump said Washington has an important relationship with NATO member and trading partner Turkey.

President Donald Trump said Tuesday that the US has not "abandoned" its Kurdish allies inside Syria, continuing to give a mixed message to Turkey.

"We may be in the process of leaving Syria, but in no way have we Abandoned the Kurds, who are special people and wonderful fighters," Trump tweeted.

This followed Trump's decision announced Sunday to remove US troops from a crucial area of the Turkey-Syria border, seemingly giving a green light for Turkey to conduct long-planned operations inside Syria against its Kurdish foes.

Given that those same Kurdish groups have fought alongside US forces against the Islamic State movement in Syria, Trump's decision was seen by prominent figures of his own Republican party as a betrayal.

Trump sought to explain his position Monday by stressing that Washington has an important relationship with NATO member and trading partner Turkey.

"So many people conveniently forget that Turkey is a big trading partner of the United States," he said in another tweet.

Trump did not say he opposed any operation by Turkey against the Kurds, but warned that "unforced or unnecessary fighting" would prompt "devastating" consequences for the country's economy.

On Monday, Trump threatened to "obliterate" Turkey's economy if it did "anything outside of what we would think is humane."