A U.S.-backed Syrian force launched a new phase of its campaign to retake the eastern part of Raqqa, the Islamic State’s de facto capital in Syria. The Syrian Democratic Forces have requested more weapons from its allies in the U.S.-led coalition in order to properly execute the mission.

The U.S. has supplied training and weapons to the Arab elements of the Syrian Democratic Forces (SDF) out of deference to NATO-ally Turkey. SDF is mostly made up of Syrian Kurds fighting with the People’s Protection Units (YPG). While the Syrian Kurds cooperate with the United States, Turkey considers their group an extension of the Kurdistan Workers’ Party (PKK), a Marxist group designated a terrorist organization by both Turkey and the United States. The latter considers the PKK a separate entity from the YPG.

Last month, the U.S. supplied the Kurdish elements of the SDF with armored sports utility vehicles for the first time, under the Trump administration. They are, however, requesting more aid, which Turkey would vehemently oppose but would be welcomed by members of Congress who support Kurdish fighters in both Iraq and Syria.

“Coalition forces provided our Arab contingent with vehicles, but the numbers are very small and we hope they will increase in the coming days,” SDF spokesman Talal Sello said Saturday, according to the Agence-France Press. “The weapons that we need to liberate Raqa are tanks, Dushkas (heavy machine guns) and armoured vehicles.”

Local SDF commander Rojda Felat told AFP that they need tanks, heavy machine guns, and more armored vehicles. She said there was a “delay” in the arrival of weapons requested but that support would be increased in the next phases of the campaign.

The aim of the new phase is to capture areas east of Raqqa, including a highway linking it to Deir Ezzor province, which is almost entirely held by ISIS.

The U.S. started its airstrike campaign in Syria in September 2014 and has backed the SDF with airstrikes. Former President Obama authorized up to 500 U.S. troops in Syria, in addition to more than 5,000 in Iraq.

The U.S. has also backed Turkey’s campaign against ISIS in northern Syria, which launched primarily to check further SDF progress in the region. The Free Syrian Army, a group of mostly Arab Syrian rebels who have cooperated with the U.S., were also involved in that endeavor.

President Trump recently signed an executive order directing his top military leaders to submit a plan in 30 days on defeating ISIS.