Syrian state media had reported earlier that the airstrike against pro-government forces in the far east of the country had caused casualties, while Iraqi officials said it had killed at least 25 Shiite paramilitaries and was just across the border from its own territory.
USA forces are also based in Tanf, southwest of Albu Kamal in the Syrian desert near the borders of Iraq and Jordan.
The UK-based war monitor said the strikes killed 40 people.
The Syrian government repeatedly denounced the criminal attacks of the Western Coalition forces, led by the United States, against the civilian population and positions of the army, which killed hundreds of residents and soldiers.
The militant group has been ousted by the Syrian and Iraqi military and US -led coalition from virtually all the territory it once controlled in Iraq and Syria, but still controls pockets of territory along the border of the countries.
The coalition's press office said it had heard reports that a strike in the area of Al-Hari had killed and wounded members of a pro-regime Iraqi group, but denied it was responsible.
The bombing raid hit Al-Hari, a town controlled by regional militias fighting in Syria's complex seven-year war alongside President Bashar al-Assad's forces.
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Pro-government forces, supported by Russian Federation and Iran, and a US-backed alliance of Kurdish and Arab fighters are both battling Islamic State (IS) militants there.
"No member of the US-led coalition carried out strikes near Albu Kamal", Major Josh Jacques, a US Central Command spokesman, told Reuters.
The U.S. has denied Syrian claims that it conducted airstrikes against regime targets in the area.
USA officials have said that many pro-regime militias that are also aligned with Iran operate in the border area between Syria and Iraq. "We're looking into who that could possibly be, but it wasn't the USA or the coalition".
Washington said the strikes were in retaliation for an attack on its own personnel and SDF forces.
Israel, alarmed about the clout of arch enemies Iran and Hezbollah, has pressed Russia, Assad's other key ally, to make sure Tehran does not entrench its military sway in Syria. "Secondly, we will take action, and are already taking action, against the attempted military entrenchment of Iran and its proxies, both close to the border and deep withinSyria".
He said the United States was an occupying power in Syria and that his state supports "any act of resistance, whether against terrorists or against occupying forces, regardless of their nationality".