Speaking to state news agency Anadolu, Tom Barrack said US President Donald Trump and his Turkish counterpart Recep Tayyip Erdogan would instruct their top diplomats to "figure out the way and end it and Congress will support an intelligent solution".

With both sides committed to drawing a line under the dispute, which has dragged on for five years, the issue could be resolved within six months, Barrack said.

"My belief is that by the year end, we have the possibility of having a solution, my belief is they're going to solve the problem," he said.

Washington imposed sanctions on Ankara in 2020 over its purchase of an S-400 Russian surface-to-air missile defence system under a 2017 law known as CAATSA, which aims to limit Russia's military influence.

It also booted Turkey out of its F-35 programme, with Washington saying the presence of the S-400 would allow the Russians to collect information on the stealth jet's capabilities -- a move that further soured ties between the NATO allies.

"All these things that have been discussed for five years, F-35s, F-16s, S400s, sanctions, tariffs... Enough. We have to put that aside, and Congress is willing to take a fresh look at it," Barrack said.

In March, Erdogan spoke to Trump about the need to finalise a deal to let Turkey buy US F-16 fighter planes and be readmitted to the development programme for F-35 warplanes.

And last month, he said he saw an end in sight to the sanctions, saying Turkey had seen them eased under Trump.

On Tuesday, Erdogan met Trump on the sidelines of a NATO summit in The Hague and called for increased defence industry cooperation with Washington, which he said could significantly boost trade between them.

"Advancing cooperation in the defence industry would facilitate achieving the goal of a $100 billion trade volume," he said.

Turkey, which wants to modernise its air force, has also been seeking to buy 40 Eurofighter Typhoons built by a four-nation consortium of Germany, Britain, Spain and Italy.