The United States has accused Russia of carrying out air strikes in southern Syria against rebels, including forces backed by the United States, that are battling the Islamic State group.
U.S. officials told Reuters and AFP on June 16 that they were "seriously concerned" about the bombings near Al-Tanf and Washington will raise the matter with Moscow.
But Russia countercharged that the United States may have a secret plan to rely in part on terrorist factions in Syria to try to unseat the Russia-backed regime of President Bashar al-Assad.
Speaking at an economic forum in St. Petersburg on June 16, Russian Foreign Minister Sergei Lavrov said that such a plan could explain the U.S. failure to persuade rebel forces it backs in Syria to distance themselves from Al-Qaeda's Al-Nusra Front, as Russia has requested, so Moscow can continue to bomb Nusra.
The United States could be "playing some kind of game here, and they may want to keep Nusra in some form and use it to topple the regime," Lavrov said, contending that the difficulty of separating the UN-blacklisted terrorist group from other rebel factions is a major reason that the war in Syria continues despite long-standing efforts to forge peace.
Lavrov said U.S. Secretary of State John Kerry denied any such secret plan to unseat Assad in a recent phone conversation. "But why then the Americans with all their potential can't force the units they have been working with to leave the territories controlled by bandits and terrorists," he asked.
For their part, the U.S. officials strongly criticized the Russian air strikes near Al-Tanf on June 16, though they did not specify what if any damage and casualties resulted from the bombings.
The U.S. officials noted that no Russian or Syrian ground forces were in the area at the time, so that ruled out an argument of self-defense to explain Russia's bombing.
"Russia's latest actions raise serious concern about Russian intentions," one official said. "We will seek an explanation from Russia on why it took this action and assurances this will not happen again."
Washington has accused Moscow of acting to prop up Assad rather than fighting IS and Nusra Front, as it claims to be doing.
Communication between the U.S. and Russian militaries in Syria has been sparse, limited to contacts aimed at avoiding an accidental clash as they carry out rival bombing campaigns.
U.S. Diplomats Slam Obama Policy
Meanwhile, a dissident group of more than 50 U.S. State Department officials criticized President Barack Obama's policy of staying out the war in Syria and said the United States should start bombing Assad's government forces in an effort to drive them to the peace table.
In a "dissident channel cable" leaked to The New York Times and The Wall Street Journal, the mid-level diplomats who are involved in Syria policy urged "targeted U.S. military strikes" to put pressure on the Syrian regime.
"The moral rationale for taking steps to end the deaths and suffering in Syria, after five years of brutal war, is evident and unquestionable," the Times quoted the internal document as saying. "The status quo in Syria will continue to present increasingly dire, if not disastrous, humanitarian, diplomatic, and terrorism-related challenges."
Their criticism came as Central Intelligence Agency Director John Brennan told Congress on June 16 that Russia's entry into the war backing Syrian forces since September has strengthened Assad's position both in the war and in the stalled peace talks.
While faced with internal dissent on June 16, the White House also was severely criticized publicly for its policies in Syria and Iraq by Senate Armed Services Committee Chairman John McCain, who lost to Obama in the 2008 presidential election.
McCain initially charged that Obama was "directly responsible" for IS-inspired attacks on Americans like the one in Orlando this week, but later said he misspoke and meant Obama's Middle East policies were to blame.
"Barack Obama is directly responsible for it, because when he pulled everybody out of Iraq, Al-Qaeda went to Syria, became ISIS, and ISIS is what it is today thanks to Barack Obama's failures, utter failures," McCain said.
"So the responsibility for it lies with President Barack Obama and his failed policies."
With reporting by Reuters, AFP, AP, and Interfax