The Syrian Kurdish fighters had originally declined the deployment of Peshmerga troops, but Erdogan told reporters in Riga, Latvia, that he'd learned Wednesday that an agreement for the reinforcement force had been reached.
However, an aide to the minister for Peshmerga in Iraq's Kurdish Regional Government told CNN that talks are ongoing.
The technical discussions involve four parties -- the United States, Turkey, the Syrian Kurds and the KRG in Iraq -- and decisions on numbers and timing are still a ways off, he said.
The reports on the Peshmerga forces came on the same day that Erdogan accused the United States of arming a group linked with terrorists, according to Anadolu, Turkey's semiofficial news agency.
Kurdish fighters have been battling alongside Free Syrian Army forces to repel ISIS forces from the Syrian Kurdish town of Kobani.
The Syrian Observatory for Human Rights, a London-based monitoring group, said Thursday that ISIS militants have taken control of the western outskirts of the border town.
This means they now surround Kobani from three sides: the east, west and south, it said.
Meanwhile, heavy clashes continue between Kurdish militia groups and ISIS militants in the northern part of Kobani, the group said.
As the clashes raged in Kobani, Erdogan said the border city, which is under the control of the armed wing of the Democratic Union Party, or PYD, is more important to Turkey than the U.S. because Turkey houses the roughly 200,000 refugees who have fled the fighting there, Anadolu reported.
He asked the U.S. to recognize the "dilemmas" there while accusing the country of arming terrorist elements among the Kurdish forces.
"Kobani is not strategic for the U.S.," he said. "It could be strategic for us only. And also, Turkey is currently accommodating all the civilians fleeing from the town. There are no civilians there."
Erdogan went on to say the U.S. was pushing arms to the PYD, which he accused of affiliation with the Kurdistan Workers' Party, or PKK, which is considered a terrorist organization by the U.S., Turkey, NATO and others.
"We had said that there are commanders from the PKK in the ranks of PYD fighting in Syria," Erdogan said. "We had said that any U.S. aid to this group is going to a terrorist organization."
There had been hopes that foreign airstrikes and airdropped supplies could help Kurdish fighters turn the tide against the ISIS militants. But the onslaught has continued.
ISIS has said that at least some of the airdropped supplies made it into its fighters' hands.
One of the 28 bundles dropped in and around Kobani on Monday drifted away from its target zone, a U.S. official said. The U.S. military said it went back and blasted it.
But a video posted on social media shows what appears to be an ISIS fighter next to a parachute bundle. He goes on to show what appears to be the contents of the bundle, including crates of hand grenades and mortar rounds.
CNN cannot independently confirm whether the items in the video are from a U.S. airdrop, but according to Anadolu, Erdogan said ISIS had seized some of the weapons.
"The rest, they also were seized by another terrorist organization, the PYD. Turkey did never lean toward such military aid and the U.S. did that despite Turkey," the news agency quoted him as saying.
Erdogan further said the Syrian groups that deserve help are the Free Syrian Army and the Peshmerga fighters, the news agency reported.
Fight for strategic hill
A Kurdish fighter and a media activist in Kobani also told CNN that ISIS militants are pushing toward the western outskirts of Kobani after attacking checkpoints manned by the Kurdish People's Protection Units, or YPG, and the Free Syrian Army.
The attacks forced them to withdraw from the strategic Tall Shair Hill area, they said.
But, they said, neither ISIS nor the YPG is able to control the western outskirts of Kobani as fighting for control of the hill rages.
Clashes also continue between ISIS and YPG fighters on the eastern outskirts of Kobani, leaving at least five Kurdish fighters dead.
ISIS militants were also killed in the clashes, but it was not immediately clear how many.
Earlier this week, U.S. airplanes dropped medical supplies and weapons into Kobani to help the city's defenders.
Rights group: Syria airstrikes killed 553
Meanwhile, a month of airstrikes in Syria by the U.S.-led coalition -- many targeting ISIS positions around Kobani -- has killed 553 people, according to the Syrian Observatory for Human Rights.
A large majority of those killed were ISIS militants, including foreigners, the group said.
However, at least 32 civilians were also among those killed between the start of the airstrikes on September 23 and October 22.
They included six children and five women, the group said in a statement Wednesday.
In total, 464 ISIS militants were killed, the Observatory said. The airstrikes also claimed the lives of 57 fighters from al Nusra Front, a rival Islamist group fighting in Syria.
The figures do not include any casualties in neighboring Iraq, where the coalition has also been targeting ISIS forces.