Rangers face competition to sign Rennes defender Mexer.
The Ibrox side have offered the Mozambique international a three-year deal, according to the Scottish Sun, with his deal expiring at the end of June.
However, a snag has emerged with Ligue 1 duo Nantes and Bordeaux, as well as Europa League semi-finalists Eintracht Frankfurt, interested in the 30-year-old.
The German side may pose the biggest threat with the club currently sitting fourth in the Bundesliga and on course to participate in the Champions League next season.
Mexer - full name Edson André Sitoe - has been with Rennes since 2014 after moving from Portuguese side Nacional where he played with Daniel Candeias. The Rangers winger had previously sent the player a message urging him to join the club.
Steven Gerrard visited the player in France recently to try and get the deal over the line, with the picture of the duo surfacing online.
Mexer has been a key individual for Rennes, playing 41 times this campaign and scoring in the club's Coupe de France success over Paris Saint-Germain.