A Syrian Kurdish sniper looks at rubble in the city of Ain al-Arab, also known as Kobani, on Jan. 30, 2015. (AP)

U.S.-backed forces fighting in northeastern Syria have encircled a key Syrian town occupied by the Islamic State, Secretary of Defense Ashton B. Carter said Thursday.

The battle to retake the town of Shaddadi is part of the Pentagon’s plan to “sever the last major northern artery between Raqqa and Mosul,” Carter said to members of a House Appropriations subcommittee. Raqqa is the Islamic State’s self-declared capital in eastern Syria, while Mosul is the extremist group’s largest stronghold in northern Iraq. Shaddadi is approximately 200 miles east of Raqqa and sits at a key east-west intersection near the Iraq border.

“This is just the most recent example of how we’re effectively enabling and partnering with local forces to help deal ISIL a lasting defeat,” Carter added, using an acronym for the Islamic State.

Carter appeared in front of Congress Thursday alongside the head of the Joint Chiefs of Staff, Marine Gen. Joe Dunford, to discuss the Pentagon’s upcoming budget. The $583 billion request includes $7.5 billion to support the U.S.-led operation against the Islamic State.

Shaddadi has been the site of heavy fighting in recent days as a group of Syrian Kurds, known as the YPG, and members of the U.S.-backed Syrian Democratic Forces have fought into the town, backed by U.S. airstrikes and, according to defense officials, U.S. military members on the ground.

A U.S. defense official who spoke on the condition of anonymity to discuss the ongoing operation said that the U.S. military has been backing forces involved in the fight with on-the-ground advising and ammunition. The official also added that clearing operations will continue in Shaddadi, but said the town and its oil assets have been reclaimed from the Islamic State.

In late December, the White House announced that it had authorized the deployment of a small detachment of special operation forces into northern Syria as a part of a presidentially approved measure to accelerate the campaign against the Islamic State.

While the official would not specify which type of U.S. units were on the ground near Shaddadi, recent posts on social media have shown advanced anti-tank weapons in the hands of forces supposedly fighting on the outskirts of the town.

According to both the Pentagon and the State Department, the weapon — a FGM-148 Javelin — has not been supplied to any U.S. backed groups in the region. The Javelin is an advanced anti-tank guided missile system with stringent export regulations and requires a moderate amount of training to use accurately.

The weapon’s presence on the front line, if confirmed, implies that U.S. and coalition advisers could be fighting very close to the front lines alongside local forces.

The Syrian Democratic Forces is composed of both Arab and Kurdish forces, many of whom participated in the defense and retaking of the Syrian town of Kobane in 2014 and 2015.

Since its formation, the Syrian Democratic Forces has been the United States’s preeminent proxy force in Syria and, as such, has been well supplied with weapons and ammunition as long as they show the ability to perform on the battlefield.

Much of their recent fighting has been relegated to northern Syria and, in the months to come, it is unclear how much support they will need to enter and seize Raqqa.

Missy Ryan contributed to this report.