The Trump administration will provide heavier weapons to Syria's Kurds as they and their allies move closer to an attack on the key Islamic State stronghold of Raqqa, US officials said on Tuesday.

The decision is meant to accelerate the Raqqa operation, but it clashes with the Turkish government's view that the Syrian Kurdish group known as the YPG is an extension of Kurdish terrorist organization that operates in Turkey.

The US sees the Kurds as its most effective battlefield partner against the Islamic State of Iraq in the Levant (Isil) in northern and eastern Syria.