"Project that we will solve something," Trump said when asked about the S-400 agreement, according to information from the White House press team.
For his part, Erdogan says that Turkey can buy missiles from the US.
"We have clearly stated to President Trump that, under appropriate circumstances, we could also acquire Patriot missiles," Erdogan said during statements at the White House.
US Senator Rick Scott said the goal of US lawmakers is to make sure that Turkey is headed for the United States and not for Russia.
Earlier on Wednesday, Scott said Turkey's relationship with Russia should worry the United States and that Congress should consider taking more action against Ankara unless Erdogan agrees to change his behavior today.
Trump and Erdogan held a meeting with Republican Senators Scott, Jim Risch, Ted Cruz, Joni Ernst and Lindsey Graham to discuss the acquisition of the S-400, the situation in Syria and other matters of mutual interest.