Republican US Senator Lindsey Graham, who has been one of the most vocal critics of President Donald Trump's decision to move US troops out of north-eastern Syria, said on Sunday he now believed "historic solutions" were possible.
In an interview with Fox News, Mr Graham said a conversation he had with Mr Trump at the weekend had fuelled his optimism that a solution could be reached where the security of Turkey and the Kurds was guaranteed and fighters from ISIS contained.
"I am increasingly optimistic that we can have some historic solutions in Syria that have eluded us for years if we play our cards right," Mr Graham said on Sunday Morning Futures.
Mr Graham said Mr Trump was prepared to use US air power over a demilitarised zone occupied by international forces, adding that the use of air power could help ensure ISIS fighters who had been held in the area did not "break out".
Senator Jim Inhofe, a Republican who chairs the Senate Armed Services Committee, said on Saturday that Mr Trump understood the need for the United States to maintain air power in the region.
"The US must retain air power to keep the pressure on ISIS, prevent our adversaries Russia and Iran from exploiting this situation and protect our partners on the ground," he said.
Mr Graham also said he believed the United States and Kurdish forces long allied with Washington could establish a venture to modernise Syrian oilfields, with the revenue flowing to the Kurds. "President Trump is thinking outside the box," Mr Graham said of Mr Trump's thinking on oil.
"The president appreciates what the Kurds have done," Mr Graham said. "He wants to make sure ISIS does not come back. I expect we will continue to partner with the Kurds in eastern Syria to make sure ISIS does not re-emerge."
Meanwhile, Russian Defence Minister Sergei Shoigu said on Monday that Moscow hopes its co-ordination with the United States and Turkey in Syria will help security and stability in the region.
Speaking during a visit to China, Mr Shoigu said the question of protecting prison facilities holding ISIS militants needed to be urgently resolved.
