BUCHAREST, ROMANIA • Biden administration officials are toughening their language toward NATO ally Turkey as they try to talk Turkish President Recep Erdogan out of launching a bloody and destabilizing ground offensive against American-allied Kurdish forces in neighboring Syria.

Since Nov. 20, after six people died in an Istanbul bombing a week before that Turkey blamed, without evidence, on the U.S. and its Kurdish allies in Syria, Turkey has launched cross-border airstrikes, rockets and shells into U.S.- and Kurdish-patrolled areas of Syria, leaving Kurdish funeral corteges burying scores of dead.

Some criticized the initial muted U.S. response to the near-daily Turkish bombardment — a broad call for “deescalation” — as a U.S. green light for more. With Erdogan not backing down on his threat to escalate, the U.S. began speaking more forcefully.

U.S. Defense Secretary Lloyd Austin called his Turkish counterpart on Wednesday to express “strong opposition” to Turkey launching a new military operation in northern Syria.

And National Security Council spokesman John Kirby on Friday made one of the administration’s first specific mentions of the impact of the Turkish strikes on the Kurdish militia, known as the Syrian Democratic Forces, that works with the United States against Islamic State militants bottled up in northern Syria.

How successfully the United States manages Erdogan’s threat to send troops in against America’s Kurdish partners over coming weeks will affect global security concerns far from that isolated

Turkish President Recep Tayyip Erdogan walks with President Joe Biden during the G-20 leaders’ summit last month in Nusa Dua, Bali, Indonesia.

corner of Syria.

That’s especially true for the Ukraine conflict. The Biden administration is eager for Erdogan’s cooperation with other NATO partners in countering Russia, particularly when it comes to persuading Turkey to drop its objections to Finland and Sweden joining NATO.

But giving Turkey free rein in attacks on the Syrian Kurds in hopes of securing Erdogan’s cooperation within NATO would have big security implications of its own.

U.S. forces on Friday stopped joint military patrols with the Kurdish forces in northern Syria to counter Islamic State extremists, as the Kurds concentrate on defending themselves from the Turkish air and artillery attacks and a possible ground invasion.

Since 2015, the Syrian Kurdish forces have worked with the few hundred forces the U.S. has on the ground there, winning back territory from the Islamic State and then detaining thousands of Is

lamic State fighters and their families and battling remnant Islamic State fighters. On Saturday, the U.S. and Kurds resumed limited patrols at one of the detention camps.

“ISIS is the forgotten story for the world and the United States, because of the focus on Ukraine,” said Omer Taspinar, an expert on Turkey and European security at the Brookings Institution and the National War College. ISIS is one widely used acronym for the Islamic State.

“Tragically, what would revive Western support for the Kurds ... would be another ISIS terrorist attack, God forbid, in Europe or in the United States that will remind people that we actually have not defeated ISIS,” Taspinar said.

Turkey says the Syrian Kurds are allied to a nearly four-decade PKK Kurdish insurgency in southeast Turkey that has resulted in the deaths of tens of thousands of people on both sides. The United States’ Syrian Kurdish allies deny attacks in Turkey.