The official, who
spoke on condition of anonymity, criticized the Russian air
strikes near al-Tanf and said no Russia or Syrian ground forces
were in the area at the time.
"Russia's latest actions raise serious concern about Russian
intentions," the official said.
"We will seek an explanation from Russia on why it took this
action and assurances this will not happen again."
British-based monitoring group the Syrian Observatory for Human
Rights said warplanes had struck a meeting of U.S.-backed forces
fighting against Islamic State in al-Tanf village, near the
al-Tanf border crossing with Iraq, killing two fighters and
wounding four others.
It said it was unclear whose planes had carried out the attack,
Washington has consistently refused to join forces with Russia
in Syria against Islamic State ever since Moscow launched its
campaign of air strikes in September last year, accusing it of
acting solely to prop up Syrian President Bashar al-Assad.
The United States has called on Assad to step down.
Communication between the U.S. and Russian militaries on Syria
has been limited to contacts aimed at avoiding an accidental
clash as they carry out rival bombing campaigns and small
numbers of U.S. forces operate on the ground.
(Reporting by Phil Stewart, Editing by Angus MacSwan)
[© 2016 Thomson Reuters. All rights
Copyright 2016 Reuters. All rights reserved. This material may not be published,
broadcast, rewritten or redistributed.