American A-10s and F-16s are conducting airstrikes in support of operations to retake a town on the Turkey-Syria border from the Islamic State, according to a defense official.

The operation to clear terrorists from Jarabulus, Syria, is Turkey's most significant involvement so far in the Syrian conflict. Turkey launched the operation, called Euphrates Shield, early Wednesday morning, sending tanks and special forces across the southern border into Syria.

Lawmakers on Capitol Hill have criticized the military for trying to retire the A-10s, pointing to the success they have had in close-air support for the anti-Islamic State campaign.

Hundreds of vetted Syrian opposition forces are also reportedly working with the Turks to free the town.

Turkish President Recep Tayyip Erdogan said that the operation is in response to a string of terrorist attacks in Turkey, including a suicide attack over the weekend that killed at least 50 people at a wedding near the Syrian border.

The new assault on the Islamic State launched during Vice President Joe Biden's visit to Turkey. Biden on Wednesday toured buildings destroyed by this summer's failed coup attempt and sought to re-affirm the relationship between Washington and Ankara after weeks of criticism that the U.S. had not been sufficiently supportive of the Turkish government.