President Donald Trump said Thursday he was "very close" to revealing his keenly awaited decision on the number of US troops he plans to keep in Afghanistan.

"We're getting close. We’re getting very close. It's a very big decision for me. I took over a mess, and we're going to make it a lot less messy," Trump said from his golf club retreat in New Jersey.

The White House has launched a review of the US plan for Afghanistan after 16 years of war, and reports suggest that Trump's national security team is divided on whether to send more troops or to pull out.