By Ellen Francis and Tom Perry
BEIRUT (Reuters) - The U.S.-led coalition have air-dropped ground forces near the Islamic State-held town of Tabqa in northern Syria, opening a new front in the campaign to capture the jihadist group's nearby stronghold of Raqqa city.
The Pentagon said on Wednesday the U.S. military had airlifted allied Syrian Arab militia fighters near Tabqa, providing them fire support in a move aimed at retaking a major dam that remains in the hands of Islamic State.
The Syrian Democratic Forces (SDF), a militia alliance including Arab and Kurdish fighters, said U.S. forces had deployed with them in the air drop, saying the operation also aimed to block any advance by government forces from the west.
A local official familiar with SDF operations said the airdrop took place on Tuesday.
The SDF, which also includes the powerful Kurdish YPG militia, is fighting to encircle Raqqa city with support from the U.S.-led coalition, including air support and backing on the ground from U.S. special forces.
The campaign to capture Raqqa from Islamic State appears to be gathering pace as an overlapping, U.S.-backed effort in Iraq is drawing closer to driving the jihadist group from Mosul.
Major Adrian Rankine-Galloway, a Pentagon spokesman, said U.S. air assets had been used to airlift members of the Syrian Arab Coalition, part of the SDF, in a bid to retake the Tabqa Dam. He did not provide details on the size of the forces moved or what type of fire support was provided.
The SDF, in a statement circulated on an official Telegram account, said: "American forces have conducted a landing operation for U.S. ground forces, along with (SDF) special forces".
The landing forces had seized four small villages in the area west of Tabqa and cut a main highway that links the provinces of Raqqa, Deir al-Zor and Aleppo, it said.
The local official familiar with SDF operations told Reuters the air-drop operation aimed to secure a crossing point for forces coming in boats across the Euphrates, which began arriving at dawn on Wednesday.
The official said the air drop was "a pioneering step".
Islamic State captured the Tabqa Dam, also known as the Euphrates Dam, and a nearby major air base at the height of its expansion in Syria and Iraq in 2014. It is located about 40 km (25 miles) to the west of Raqqa city.
The head of the YPG told Reuters last week a final assault to capture Raqqa city from IS would begin at the start of April. The Pentagon said a decision had yet to be taken.
Turkey is pressing Washington for a role in the Raqqa campaign. Ankara is concerned about the growing influence of the YPG, seeing it as an extension of the Kurdistan Workers' Party (PKK), which has fought a three-decade insurgency in Turkey.
The SDF cut the last main road out of Raqqa earlier this month, narrowing in on the city from the north, east and west.
The only way in or out of Raqqa now is over the Euphrates River that borders the city to the south.
Air strikes by the U.S.-led coalition near Raqqa have escalated this month, the Syrian Observatory for Human Rights said. The Britain-based war monitoring group said an air strike killed at 33 people near Raqqa when it hit a school sheltering displaced people on Monday.
The Observatory said it believed the strike was carried out by the U.S.-led coalition.
The Pentagon said on Wednesday that there were no indications that a strike near Raqqa had hit civilians, but that it would carry out further investigations.
Islamic State is losing ground to three separate campaigns in northern Syria - by the SDF, by the Russian-backed Syrian army and by Turkish-backed Syrian rebels.
(Additional reporting by Idrees Ali; Editing by Tom Heneghan)