The US-led coalition in Syria has mounted an airstrike against government forces in response to an attack on its local allies.
Syrian rescue workers and activists say the death toll from ongoing government strikes on the opposition-held region near the capital Damascus has risen to at least 35.
Veale said no coalition or U.S. personnel had been killed or wounded in the engagement but that one member of the Syrian Democratic Forces was wounded.
Veale said the coalition suspected that pro-regime forces were attempting to seize territory, including lucrative oil fields, that the Syrian Democratic Forces had liberated from ISIS in September.
The river acts as a de-confliction line between the coalition and Russian and Syrian forces. A U.S. official said that "20 to 30 artillery and tank rounds landed within 500 meters" of the SDF headquarters.
The U.S. has long supported the Syrian Democratic Forces, often characterizing the group as "moderate", and crediting them for playing a significant role in the defeat of ISIS in Syria.
According to the Kremlin, the attack American forces repelled was nothing more than "a reconnaissance party made up of Syrian militias" that crossed the Euphrates River (which serves as a deconfliction line between American and Russian backed forces) to hunt down remaining ISIS positions.
They "were likely seeking to seize oilfields in Khusham that had been a major source of revenue for Daesh from 2014 to 2017", he said, using the Arabic acronym for ISIS.
"Now they say that their presence will continue until they are convinced that a stable political settlement process, leading to regime change, has begun in Syria", he said.
The SDF and the coalition targeted the attacking forces with air and artillery strikes after "20 to 30 artillery and tank rounds landed within 500 metres (yards) of the SDF headquarters location", the official said.
The Britain-based Syrian Observatory for Human Rights said 56 people, including 10 children, were killed on Thursday.
The minister's statement followed a US-led coalition attack that killed 100 Assad regime troops.
The officials said that Turkish President Recep Tayyip Erdogan and his Russian counterpart Vladimir Putin agreed to the summit during a telephone call on Thursday.
CENTCOM said the attack occurred eight kilometers (five miles) east of the "Euphrates River de-confliction line", referring to a boundary agreed to by Russian Federation and the U.S., with the former's area of operations to the west of the river and the latter's to its east.
Neither U.S. officials nor the U.S. -backed coalition have offered details on the identity of attacking forces.
Russia's Ministry of Defense indicated Thursday that the pro-regime forces had not been coordinating with Russian officials in the area.
"It's straightforward for the regime - it wants to take all of Syria", said Hassan, a senior fellow at the Tahrir Institute.
"The United States believes that free and transparent elections, to include the participation of the Syrian diaspora who have been displaced - all those who were forced to flee the conflict - will result in the permanent departure of Assad and his family from power", Tillerson said.
Syrian state media characterized the event differently, saying the USA had bombed "popular local forces fighting" ISIS, and that it was a U.S. "attempt to support terrorism". "Plans for the actual partition of Syria do exist, and we are aware of that". The US also shot down a pro-regime drone after it dropped a munition in the vicinity of US troops in Syria.