Russia's Foreign Minister Sergey Lavrov Monday dismissed as "counterproductive" an announcement by Washington that it could take extra measures to defend U.S.-allied fighters in Syria. At a news conference in Qatar, Lavrov condemned comments by the White House that it could take "additional steps" to protect allies in Syria and warned President Bashar Assad's regime not to impede their actions. "We believe it's counterproductive to announce publicly that some U.S.-trained armed groups ... will be under the protection of the coalition's air forces," Lavrov said. "And that to protect these groups this air force would be authorized to strike at any forces which may – may – be considered a hindrance to the work of this group." Lavrov added that the matter had been raised with U.S. Secretary of State John Kerry when they met earlier Monday in Qatar's capital Doha. Earlier, White House spokesman Josh Earnest said Syria "should not interfere" with operations by U.S.-trained forces, warning that "additional steps" could be taken to defend them, raising the prospect of strikes against the regime. In another apparent criticism of Washington, Lavrov said: "We are seriously concerned about the continuing crisis in Syria and the humanitarian disaster that has broken out in the country, and are in favor of an immediate end to external intervention in the Syrian crisis." Lavrov said the matter had been raised with Kerry. Both Lavrov and his American counterpart were in the Gulf to hold a series of talks on wide-ranging matters including not only Syria, but also issues such as the Iran nuclear deal, "terrorism" and Yemen. Lavrov held a tripartite discussion with Kerry and Saudi Foreign Minister Adel al-Jubeir. Turkish media quoted President Recep Tayyip Erdogan as saying that Russian President Vladimir Putin is having a change of heart on the Kremlin's wholehearted support for Assad and may "give up on him" in the future. When asked if Putin could be persuaded not to support Assad, Erdogan said he saw his counterpart as "more positive" during a face-to-face meeting in the Azerbaijani capital of Baku in June and in subsequent telephone talks. "Putin's current attitude toward Syria is more encouraging than before," Erdogan told a group of journalists on his presidential jet as he returned from a trip to Asia. "He is no longer of the opinion that Russia will support Assad to the end. I believe he can give up Assad," he was quoted as saying by the Daily Sabah and Sabah dailies. Turkey and Russia stand on opposing sides over the crisis in Syria, with Ankara one of the fiercest critics of Assad and Moscow one of his few remaining allies. U.S. officials said late Sunday that the United States has decided to allow airstrikes to defend Syrian rebels trained by the U.S. military from any attackers, even if the enemies hail from forces loyal to Assad. The decision by President Barack Obama, which could deepen the U.S. role in Syria's conflict, aims to shield a still-fledging group of Syrian fighters armed and trained by the United States to battle ISIS militants – not forces loyal to Assad. But in Syria's messy civil war, ISIS is only one of the threats to the U.S. recruits. The United States would also provide defensive support to repel any attackers. U.S. officials have long played down the idea that Assad's forces – which have not fired on U.S.-led coalition aircraft bombing ISIS targets in Syria – would turn their sights on the U.S.-backed Syrian rebels. But they cannot rule out the possibility, perhaps in an unintentional clash.