LONDON — The battle for control of Libya threatened to escalate further this week as Turkey said it might intervene to stop the Russian-backed forces now closing in on Tripoli, the capital.
In comments to Turkish television networks on Monday night and again on Tuesday, President Recep Tayyip Erdogan pointedly raised the possibility that Turkey might send troops to counter the Russians if the United Nations-recognized government headquartered in Tripoli formally requested it.
“In case of such an invitation, Turkey will decide itself about what kind of initiative to undertake,” Mr. Erdogan said Monday. On both Monday and Tuesday he referred explicitly to the possibility of “sending soldiers” or “our personnel.”
Mr. Erdogan, for commercial and political reasons, has emerged as the last significant patron of the beleaguered Tripoli government. His blunt talk of a new military intervention underscored the perilousness of the situation now facing the Tripoli government, which is under a tightening siege by Russian forces backing the militia leader Khalifa Hifter.
Officials of Tripoli’s so-called Government of National Accord quickly accepted Mr. Erdogan’s offer. “The G.N.A. welcomes ALL international support,” Mohamed Ali Abdullah, an adviser for United States affairs to the Tripoli government, wrote in a text message.
Libya is a strategic prize with vast oil reserves and a long Mediterranean coastline.
But eight years after a NATO intervention helped topple Col. Muammar el-Qaddafi during the Arab Spring revolt, the country remains mired in chaos. The bedlam has turned its beaches into a departure point for tens of thousands of Europe-bound migrants and its deserts into a haven for bands of militant extremists.
Over the last three months, Russia has transformed Libya’s simmering civil conflict by deploying large numbers of fighters in what increasingly appears to be a determined push to help Mr. Hifter capture the capital.
Mr. Hifter, 76, had been waging an on-again, off-again fight to take Tripoli for more than five years, with no success. His most recent assault, launched April 4, left his forces stalled for more than five months on the southern outskirts of the city.
Now, however, the heavy Russian support has enabled Mr. Hifter’s forces to renew their advance into the city. Over the weekend, they captured most of the neighborhood of Salah el-Deen, one of their biggest gains in months.
“The momentum has definitely shifted,” said Frederic Wehrey, a scholar at the Carnegie Endowment for International Peace who recently returned from a visit to the front. He saw signs of exhaustion among some of the city’s defenders, he said.
“If morale snaps, it is a terrifying thing,” Mr. Wehrey said. “And who knows when it is going to give way?”
A collapse of the government would most likely mean a prolonged period of bloody street fighting inside the city, with years of insurgency by regional militias opposed to Mr. Hifter and now facing revenge. The turmoil would almost certainly set off new waves of internal and external migrants fleeing, analysts and diplomats say.
For Washington, Mr. Wehrey argued, allowing Russian forces to establish dominance in Libya, as they already have in Syria, would also “seriously damage whatever U.S. credibility is remaining in the Middle East.”
“Russia is basically pushing on a door that has been creaking open for a while,” he said. The United States has largely withdrawn from Libya while the European powers have been divided over how to approach it.
Since the United States began to pull back after the 2011 NATO intervention, an array of regional powers — all Western-armed American partners — have plunged into the vacuum, providing weapons and support to favored clients doing battle with one another. The United Arab Emirates, Egypt, Saudi Arabia and France eventually lined up behind Mr. Hifter, betting that his authoritarian style could restore stability.
Turkey, in part because of its rivalry with the Emirati-Egyptian-Saudi bloc in a regional cold war, has become the only significant military backer of the Tripoli government.
The United States, along with the other Western powers, also publicly supports the Tripoli government and a United Nations-sponsored peace process on the unity government, but only Turkey has provided military support.
Washington, in practice, has sent mixed signals.
United States officials, who say the Russian forces in Libya now include uniformed troops as well as mercenaries, have called their presence “incredibly destabilizing” and warned of “the specter of large-scale casualties among the civilian population.”
But the National Security Council official overseeing Libya, Victoria Coates, met with Mr. Hifter two weeks ago to discuss peace talks, granting him a new level of recognition from the White House.
When Mr. Hifter began his advance, in April, Secretary of State Mike Pompeo issued a statement condemning the assault on Tripoli, but the White House released a statement days later saying President Trump had called Mr. Hifter to commend his fight against “terrorism.”
This week, United States military officials said that they believed a Russian air defense system installed in Libya had brought down an American surveillance drone. Gen. Stephen J. Townsend, chief of the United States Africa Command, said in a statement on Monday that the forces that brought down the drone had not realized it was American.
“But they certainly know who it belongs to now,” he said, “and they are refusing to return it. They say they don’t know where it is, but I am not buying it.”
Before the Russian intervention this fall, the Libyan strife had consisted mainly of simmering, low-intensity warfare.
A total of a few hundred untrained fighters at any one time clashed in a handful of deserted districts on the edge of Tripoli, as armed drones fired down from above. Mr. Hifter’s forces flew Chinese-made drones furnished by the United Arab Emirates, and the Tripoli forces countered with less potent Turkish models.
But all that began to change as the Russian forces arrived earlier this fall.
By October, as many as two hundred Russian mercenaries had arrived, and within weeks the number grew to more than a thousand. They brought with them more advanced air power, better coordinated air support for ground troops, and guided artillery, as well as trained snipers.
With their help, Mr. Hifter’s forces now control the air. The Tripoli government’s Turkish drones seem to have disappeared from the sky, presumably damaged or destroyed by Mr. Hifter’s allies.
“The Tripoli forces have nothing in the air now,” said Wolfram Lacher, a scholar of Libya at the German Institute for International and Security Affairs. “Everyone is waiting for the new Turkish equipment to arrive.”
Mr. Erdogan spoke for years about avoiding conflicts in the region. But his talk of intervening in Libya follows a Turkish incursion into northern Syria two months ago, as Turkish troops moved against American-backed, Kurdish-led militias there and struck an accommodation with the Russian forces active in the country.
In the television interview on Monday night, Mr. Erdogan pledged to appeal personally to President Vladimir V. Putin of Russia at a meeting in January.
Calling Mr. Hifter “an outlaw,” Mr. Erdogan said, “On the Hifter issue, I don’t want it to give birth to a new Syria in relations.”
He added, “I believe Russia will also review its existing stance toward Hifter.”
Mr. Erdogan has more at stake, though, than stability in Libya.
His comments about a possible military intervention come just days after Ankara signed a deal with the Tripoli government that would give Turkey drilling, pipeline and other maritime rights over an expanded portion of the Mediterranean Sea between the countries. That set off outrage from Greece and Europe, but gave Turkey a new financial stake in the Tripoli government.
The president’s statements, Mr. Lacher said, “suggest that this agreement is so important to the Turks that they are willing to do whatever it takes to stop Hifter from winning.”