ISTANBUL — The latest American plan to aid Syrian fighters battling the Islamic State hit a bump on Wednesday, as Turkish officials summoned the American ambassador to express concern that the United States was providing new support to Kurdish militants in Syria that Turkey considers a primary enemy.
But in a twist, Turkey also summoned the Russian ambassador over concerns thatRussia, too, was helping the Kurds. This could suggest that there is at least one area — supporting Kurdish militias — where American and Russian interests inside Syria may converge. Or it could be developing into another point of contention, as the two sides compete for the Kurds’ affections.
That would add another layer of complexity to the tangled battlefield inside Syria and potentially upend the American relationship with the Kurdish militias, the United States’ most important on-the-ground partner inside Syria in the fight against the Islamic State.
The Turks were reacting in part to the United States’ airdropping of 50 tons of ammunition over the weekend to members of an Arab-Kurdish coalition that the United States wants to build up so it can take on the Islamic State in its stronghold in the northern Syrian province of Raqqa. American officials say the equipment is meant only for the Arab fighters in the coalition. But multiple fighters on the ground say that in practice, they operate under Kurdish auspices.
Turkey is generally concerned about the growing American partnership with the Syrian Kurdish militias, which Turkey’s government in Ankara links to Kurdish fighters inside the country who have long fought the Turkish state.
Analysts say it is also possible that the Turkish reaction could be a pro forma protest for domestic political consumption, a month or so before an election in which feelings are running high over the Kurdish issue. But it would not be the first time that the United States and Turkey appeared to agree on an approach against the Islamic State, also known as ISIS or ISIL, only to run quickly into disagreements.
After the allies announced over the summer that Turkey would start airstrikes against ISIS in Syria, it carried out some, but primarily struck Kurdish militants in Iraq. And plans to work together to create an “ISIS-free zone,” or buffer zone, in the northern province of Aleppo appear to have been quietly shelved after the goals were described very differently by American and Turkish officials.
American efforts to train Syrian Arab insurgents to fight ISIS have run into other pitfalls; an earlier Pentagon effort was canceled last week, long after it was widely acknowledged to be a failure.
American officials acknowledged on Wednesday that Turkish officials were especially livid at the timing of the airdrop: so soon after the devastating suicide blasts on Saturday that killed nearly 100 people, and just before the elections. Although the Turkish authorities suspect ISIS was behind the bombings, public sensitivities are still running high over militants of any stripe.
There is also a sense that despite Turkey’s recent commitment to open its Incirlik air base and join other allied warplanes in striking ISIS targets, the United States will do what it wants with its allies in Syria, when it wants, no matter the upset it may cause, the officials said.
Further complicating the picture in northern Syria, Iranian television reported that the Syrian government was on the verge of launching a major new offensive, backed by Russian warplanes and Iranian-sponsored militias on the ground, in Aleppo Province, just west of Raqqa.
That would be an expansion of another Russian-backed, Syrian ground offensive unfolding further south in Hama Province. Several reports, including in the pro-Hezbollah Lebanese newspaper Al Akhbar, said the expanded government offensive would include Iran’s largest direct battlefield intervention to date, involving hundreds, and possibly thousands, of Iranian troops.
Iran has been the Syrian government’s most important ally during more than four years of war, keeping President Bashar al-Assad afloat through loans and military support, including advisers embedded with units in the field and the critical participation of Iranian-sponsored militias such as Hezbollah and Iraqi Shiite groups.
But it has long denied direct military involvement except for the presence of Iranian military advisers on some fronts; Iranian news media did, however, confirm the death of a prominent Iranian general in Aleppo last week.
Perhaps more significant in the long run is the potential competition between Russia and the United States for the allegiance of the Syrian Kurds.
The United States has long backed the Syrian Kurdish militia, known as the People’s Protection Units, or Y.P.G., going back to the battle last year for the city of Kobani, but it now appears that Russia may be cozying up to the group.
Reports have emerged in recent days that Russian officials have met with Salih Muslim, the leader of the Democratic Union Party, whose armed wing is the Y.P.G. Russia has historic ties to the group stretching back to Soviet days. The Y.P.G. is the Syrian offshoot of the Kurdistan Workers’ Party, or P.K.K., the group that began waging an insurgency against Turkey in the 1980s, a conflict that recently resumed after failed peace talks.
“Turkey will not accept any cooperation with terror groups fighting against Turkey,” Ahmet Davutoglu, Turkey’s prime minister, said at a news conference on Wednesday in Istanbul. “We have shared this with the U.S. and Russia.”
An official with the Foreign Ministry confirmed that the Russian and American ambassadors met separately on Tuesday with Turkish officials.
Mr. Davutoglu raised concerns that the American-supplied arms could later be transported to Turkey to be used by the P.K.K., comments that signaled a newly aggressive stance by Turkey toward the growing American partnership with the Syrian Kurds.
In the past, Turkey has largely acquiesced under pressure from the United States. In return, American officials have voiced support for Turkey’s war with the P.K.K. But they have also tried to draw a distinction between the P.K.K. and its Syrian counterparts, both the political and military arms, saying they should be dealt with separately.
Now, it appears, Turkey’s tone is changing. An article in the pro-government news media even suggested the P.K.K.’s Syria affiliate was trying to obtain from United States stockpiles Stinger missiles that its militias would use to shoot down Turkish aircraft.
“Turkey will not tolerate arms aid to groups linked to the P.K.K.,” Mr. Davutoglu said Wednesday.
Also Wednesday, allies of the Syrian government reported that it was planning major new ground operations, expanding its new Russian-backed offensive northward to Aleppo, with the help of allied fighters from the Lebanese militia Hezbollah and possibly even Iranian ground forces.
The aim, the reports said, was to regain government control of the spine of territory going from the central province of Homs northward through Hama, Idlib and all the way to Aleppo Province on the Turkish border.
Advancing in Aleppo would mean a northward expansion of Syrian forces’ first ground operation taking advantage of Russian airstrikes, which began last week in the provinces of Idlib and Hama. New operations will also begin to the south, in Homs Province, Iran’s state television said.
After three video conference calls and a lot of trans-Atlantic name-calling, American and Russian officials are completing safety protocols for their respective pilots in the skies above Syria, Pentagon officials said Wednesday.
The last conference call took place Wednesday, and a Defense Department official said afterward that a final pact is expected in the coming days. The discussions were initially billed as “deconfliction” talks, but the subject has since been downgraded to “specific safety procedures,” lest anyone think that the United States is cooperating with Russia’s bombing campaign in Syria.
American officials say the talks are focused on issues like what language and radio frequencies American and Russian pilots will use to communicate with one another.