The United States said Thursday that it supported Turkey after it sent its military into Iraq to strike at Kurdish rebels in retaliation for an attack that killed 24 soldiers.

“We very clearly support Turkey’s right to self-defense,” State Department spokesman Mark Toner told reporters.

“At the same time, there needs to be cooperation between Turkey and Iraq and there is in fact a mechanism in place for that cooperation to occur, the Trilateral Security Dialogue,” he said.

Toner was referring to a committee set up in 2008 by Ankara, Baghdad and Washington to take up the issue of the Kurdistan Workers’ Party (PKK), long an irritant in Turkey’s ties with Iraq and by extension the United States.

Turkey said it was sending in 22 battalions against PKK forces in Iraq, using both air and ground power. Analysts said the incursion entailed 10,000 to 15,000 troops.

President Barack Obama on Wednesday condemned the “outrageous terrorist attack” by the PKK and officials said that Secretary of State Hillary Clinton spoke by telephone to Turkish Foreign Minister Ahmet Davutoglu.

The PKK took up arms in Kurdish-majority southeastern Turkey in 1984, sparking a conflict that has claimed about 45,000 lives.