A U.S. service member joins a commander from the Kurdish People’s Protection Units as they inspect the damage at YPG headquarters after it was hit by Turkish airstrikes near Malikiya, Syria, on April 25. (Reuters)

The Turkish government gave the United States less than an hour’s notice before conducting strikes on partner forces in Iraq and Syria, the U.S. military said on Wednesday, stepping up its criticism of airstrikes the United States said endangered American personnel.

Col. John Dorrian, a U.S. military spokesman, said the lead time failed to provide adequate notice to reposition American forces or warn Kurdish groups with whom the United States is partnering against the Islamic States.

“That’s not enough time. And this was notification, certainly not coordination as you would expect from a partner and an ally in the fight against ISIS,” he said, using an acronym for the Islamic State.

American officials expressed indignation at the Turkish bombing, which killed as many as 20 Kurdish fighters in Syria and, according to the U.S. military, five Kurdish peshmerga troops in a coordinated attack across the border in northern Iraq. According to the Turkish government, both attacks targeted members of the Kurdistan Workers’ Party (PKK), which both Ankara and Washington consider a terrorist group.

A defense official, speaking on condition of anonymity to discuss operations, described the assault as a “massive, highly coordinated attack” involving more than 25 strike aircraft.

In Syria, the Turkish jets targeted leadership sites used by the Syrian Democratic Forces (SDF), a Kurdish-dominated force that has emerged as the United States’ primary military partner in Syria, according to a second U.S. official. Turkey has objected to that alliance because, it says, the SDF’s largest component, the People’s Protection Units (YPG), is a PKK affiliate.

Despite the Turkish position, Dorrian signaled the United States would continue its support for the SDF, as it would for Iraqi government troops across the border.

“These are forces that have been integral in fighting ISIS. They’ve been reliable in making progress against ISIS fighters under very difficult and dangerous conditions,” he said. “They have made many, many sacrifices to help defeat ISIS and that keeps the whole world safer. So that is our position on that.”

In Syria, U.S. troops were within six miles of the targeted area, far enough to be out of danger but close enough to cause concern about the potential for unintended bloodshed, Dorrian said. While U.S. forces were not as close to the Turkish target area in Iraq, U.S. officials expressed criticism of the fact that the strike was conducted without the consent of the Iraqi government.

Dorrian spoke hours after the Turkish embassy in Washington issued a statement from the country’s Foreign Ministry detailing what it said were the steps Turkey took to make the United States and other countries active in Syria aware of its plans, saying the United States and Russia were “duly informed through both military and diplomatic channels.”

That included, the ministry said, notifying the U.S. air command center in Qatar and speaking with the head of the U.S. military. A spokesman for Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, could not immediately confirm whether Dunford had spoken with the Turkish officer.

U.S. officials provided a different characterization of what occurred, saying that American personnel had immediately expressed their objections to the Turkish plans when they were notified.

Adding to the U.S. frustration, Dorrian said Turkey had provided only general information ahead of time about where the strikes would occur and who they would target. “Less than an hour of notification is an inadequate amount of time to have our forces leave the ops box area that was identified … which was a very large ops box,” he said, referring to the area in which U.S. forces are operating. “So it was an unsafe way to conduct operations.”

Dorrian said that the United States has sent military personnel to the affected site in Syria to assess the damage to SDF forces.

Thomas Gibbons-Neff and Karen DeYoung contributed to this report.