WASHINGTON ¨C Republican Sen. Lindsey Graham, who has been one of the most vocal critics of President Donald Trump¡¯s decision to move U.S. troops out of northeastern Syria, said on Sunday he now believed ¡°historic solutions¡± were possible.

In an interview with Fox News Channel, Graham said a conversation he had with Trump over the weekend had fueled his optimism that a solution could be reached where the security of Turkey and the Kurds was guaranteed and fighters from Islamic State 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,¡± Graham said.

Graham said Trump was prepared to use U.S. air power over a demilitarized zone occupied by international forces, adding that the use of air power could help ensure Islamic State fighters who had been held in the area did not ¡°break out.¡±

Sen. Jim Inhofe, a Republican who chairs the Senate Armed Services Committee, said on Saturday that Trump understood the need for the United States to maintain air power in the region.

¡°The U.S. 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 in a statement. ISIS is an acronym for Islamic State.

Graham also said he believed the United States and Kurdish forces long allied with Washington could establish a venture to modernize Syrian oil fields, with the revenue flowing to the Kurds. ¡°President Trump is thinking outside the box,¡± Graham said of Trump¡¯s thinking on oil.

¡°The president appreciates what the Kurds have done,¡± Graham added. ¡°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.¡±

Graham, referring to the Kurdish fighters in the region, had previously warned that Trump¡¯s decision to pull out U.S. troops would lead to their ¡°destruction.¡±