The Pentagon has suggested it will carry out air strikes against Islamic State (IS) militants within Syria’s so-called "de-escalation zones," despite Russia’s announcement that the areas would be closed to U.S.-led coalition military aircraft.
A Pentagon spokesman, Major Adrian J.T. Rankine-Galloway, said on May 5 -- just hours before the Russian-backed safe zone plan was to be implemented -- that "the coalition will continue to target [IS militants] wherever they operate to ensure they have no sanctuary."
Rankine-Galloway noted that the U.S. government is not party to the safe-zone agreement that was signed by Russia, Turkey, and Iran on May 4 at Syria peace talks in Astana, Kazakhstan.
The Pentagon spokesman also said the United States continues to "effectively de-conflict coalition operations. However, we are not going to discuss the specifics of how we de-conflict operations in the highly congested and complex battlespace in Syria."
Russian state-run TASS news agency reported that Foreign Minister Sergei Lavrov had spoken by phone with U.S. Secretary of State Rex Tillerson about the de-escalation arrangement, but it did not provide details.
The safe-zone agreement was due to be implemented in Syria at midnight on May 6.
Earlier on May 5, Russia's chief representative at Syria peace talks in Astana said the safe zone areas will be closed to warplanes of the U.S.-led coalition.
"In the de-escalation zones, aviation operations -- especially by the forces of the international coalition forces -- are absolutely not envisaged, with or without prior notification. This question is closed," Russian envoy Aleksandr Lavrentyev said.
However, Lavrentyev said later on May 5 that U.S.-led coalition aircraft would still be able to operate against IS militants in specific areas. He did not clarify whether that included IS targets inside the designated safe zones.
Lavrentyev also has said neither Russian nor Syrian warplanes would fly within the de-escalation zones unless Syrian opposition fighters attack Syrian government forces.
But he said they will continue to attack IS militants in areas outside of the safe zones.
Meanwhile, Russia's military said on May 5 that it will continue fighting IS extremists and the Al-Qaeda linked affiliate previously known as Al-Nusra, including inside the "de-escalation zones."
The Russian announcements have raised concerns among Syria's armed opposition groups, whose members say such declarations have been used in the past by President Bashar al-Assad's government to enable his Russian-backed forces to strike anywhere and claim they are attacking terrorists.
The pact was opposed by the High Negotiations Committee (HNC), the main Syrian opposition umbrella group backed by the United States and Saudi Arabia.
In a statement issued on May 5, the HNC rejected Iran’s role as a guarantor of the plan. It also said only the United Nations should be entrusted with talks on the Syrian conflict, and it urged against moves that would "partition the country through vague meanings of what has been called...'de-escalation' zones.'"
The HNC also said the safe-zone plan would allow Syrian government forces to achieve military goals that they could not on the battlefield by neutralizing forces in rebel-held territories.
Senior Russian military commander Sergei Rudskoi said on May 5 that Russian military officials would meet "with U.S. colleagues in the near future" to discuss Russia’s return to full-scale participation in an agreement aimed at direct conflict with each other in Syrian airspace.
Russia suspended its participation in the agreement in early April after U.S. President Donald Trump ordered a cruise-missile strike against a Syrian air base in response to what Washington said was a chemical attack against civilians by Assad’s forces.
Separate air strike campaigns by Russia and the United States have caused tension in the past two years.
The United States reacted cautiously to the agreement, saying that it "supports any effort that can genuinely de-escalate the violence in Syria" but expressing concern about Iran's role as a cease-fire guarantor and saying Russia must ensure compliance by the Syrian government.
State Department spokeswoman Heather Nauert said the United States "supports any effort that can genuinely de-escalate the violence in Syria, ensure unhindered humanitarian access, focus energies on the defeat of ISIS and other terrorists, and create the conditions for a credible political resolution of the conflict."
However, the State Department said it continues to have concerns about "the involvement of Iran as a so-called 'guarantor.' Iran’s activities in Syria have only contributed to the violence, not stopped it, and Iran’s unquestioning support for the Assad regime has perpetuated the misery of ordinary Syrians.
"In light of the failures of past agreements, we have reason to be cautious. We expect the regime to stop all attacks on civilians and opposition forces, something they have never done. We expect Russia to ensure...compliance" by Syrian President Bashar al-Assad's government, she said.
UN Secretary-General Antonio Guterres cautiously welcomed the agreement on May 4 but suggested it is important to see results on the ground.
Guterres "is encouraged by the agreement...to de-escalate violence in key areas in Syria," his spokesman, Stephane Dujarric, said in a statement on May 4.
"It will be crucial to see this agreement actually improve the lives of Syrians," he added.
Within safe zones that are being set up, the memorandum signed in Astana by Russia, Turkey, and Iran calls for a cease-fire, a ban on all overflights, rapid deliveries of humanitarian aid to the designated areas, and the return of refugees.
The Astana safe-zone plan for Syria calls for setting up four "de-escalation zones" in northern, central, and southern Syria, where Assad’s forces are fighting rebels in a war that has killed some 400,000 people since 2011.
They would be surrounded by checkpoints manned by opposition and government troops.
Foreign troops also could be deployed in observer roles.