The Bundesliga outfit took to Twitter this afternoon as the squad continue preparations for their Bundesliga opener at home to Hoffenheim on August 18, but they freely admitted that Willems was absent from the session.
The 25-year-old Dutchman has been a long-term target for the Magpies, who were first linked with a move for the defender back in January 2016 while he was a PSV Eindhoven player.
There is a suggestion the move could consist of an initial loan deal with an option to buy the player at the end of the 2019-20 season.
The Rotterdam-born full-back joined Frankfurt in July 2017, and was part of the side that triumphed in the German Cup final the following year after a 3-1 win over Bayern Munich in Berlin.
New Toon manager Steve Bruce is keen to bring in another left-back during the current transfer window to provide competition for local boy Paul Dummett, who became a regular first-team fixture under previous boss Rafa Benitez.
Willems could form one-half of a double transfer announcement at St James’ Park this weekend, with French winger Allan Saint-Maximin also expected to complete a move to Tyneside from Nice over the next 24 to 48 hours.
The pair will become Bruce’s second and third signings of the summer transfer window following the arrival of Brazilian striker Joelinton from Hoffenheim for a club-record fee last month.
The striker, who was handed the club’s famous number nine shirt ahead of the new campaign, has made an instant impact in pre-season and been described by Borussia Dortmund defender Manuel Akanji as the toughest opponent he faced last season.