"We can easily say that there is a softening in CAATSA,," he told reporters while returning from a European summit, referring to US sanctions legislation.

In 2020, Washington imposed sanctions on Ankara 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.

The move soured ties between the two NATO member countries.

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.

Erdogan said Turkey had raised the sanctions issue with Trump and his newly-appointed envoy to Ankara, Tom Barrack

"With my friend Trump taking office, we have achieved a more open, more constructive and more sincere communication on these issues," Erdogan added, saying Turkey valued "every positive step in this direction".

"I believe we will overcome the CAATSA process much faster. As two great NATO allies, there should be no restrictions or obstacles in the field of defence between us," he said.

Turkey's partnership with the United States was "of vital importance for the establishment of stability in our region and the world" he 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.

Turkey has been seeking to modernise its airforce, and has been seeking to buy 40 Eurofighter Typhoons which are built by a four-nation consortium grouping Germany, Britain, Spain and Italy.