US combat airlift marks deepening involvement in Syria

The United States is deepening its involvement in the war against the Islamic State after an unprecedented US airlift of Arab and Kurdish fighters to the front lines in northern Syria, supported by the first use of US attack helicopters and artillery in the country.

The US forces didn't engage in ground combat, but the offensive suggests the Trump administration is taking an increasingly aggressive approach as it plans an upcoming assault on the extremists' self-declared capital of Raqqa. In addition to using helicopters to ferry rebels into combat near the Tabqa Dam on the Euphrates River, the US also flew two Apache gunships and fired Marine 155mm artillery.

US officials said the operation inserted Syrian Arab and Kurdish fighters behind IS lines west of Raqqa, subjecting the US personnel to a degree of risk previously avoided in Syria. The mission was focused on recapturing the dam, the nearby town of Tabqa and a local airfield.

By design, the operation is coinciding with a potentially climactic battle for Mosul, the main IS stronghold in Iraq. Together, the battles reflect a US strategy of presenting IS with multiple challenges simultaneously.

The US airlift, known in military parlance as an air assault, marked a new level of commitment to Syria's Kurds, whose partnership with the US has prompted difficult discussions with Turkey. The US-Nato ally sees the Kurdish fighters as a national security threat because of their links to militants inside Turkey.

The Kurdish-led Syrian Democratic Forces confirmed the US airlift and said their fighters seized four villages south of the Euphrates and cut the main artery between Raqqa and northwestern Syria. Tabqa lies 45km, west of Raqqa.

In Washington, the US hosted top officials from 68 nations for a meeting on accelerating the fight against IS in all its dimensions.

Secretary of State Rex Tillerson told the coalition's first ministerial gathering since President Donald Trump took office that the US was still refining its strategy, but was clear about US priorities.

While that assessment appeared shared, some participants were hoping to hear more about strategy changes. As a candidate, Trump spoke boldly about overhauling former President Barack Obama's cautious approach to fighting IS. As president, Trump has moved more cautiously.

At a Senate hearing Wednesday, Defence Secretary Jim Mattis told a Senate committee that the Trump strategy was still in "skeleton" form.

Mattis and other officials have strongly suggested the plan will preserve the central feature of the Obama administration's approach, namely the idea of advising and enabling local forces to fight rather than doing it for them. But as IS appears to lose strength and territory in Iraq and Syria, the US is likely to bolster its support and perhaps send small numbers of additional troops.

The US now has about 1,000 troops in Syria. It has at least 7,000 in Iraq.