Martinez – who arrived in Milan from Racing Club in 2018 – has been tipped to swap Serie A side Inter for Barca at the end of the 2019-20 coronavirus-hit season.
The Argentina forward had scored 16 goals prior to the campaign being halted in March due to the COVID-19 pandemic but he has only netted once in seven games since the restart amid the speculation.
Bartomeu provided an update on Martinez and Barca's transfer plans, with the club set to be dethroned by bitter rivals Real Madrid in LaLiga.
"The coming market will be very different. The big clubs will be limited by economic problems, but Barca are always a market-mover," Bartomeu told TV3.
"In Lautaro's case the negotiation is halted right now. We spoke to Inter a few weeks ago. We are in an assessment phase.
"We have spoken with Inter about Lautaro, but not recently. We will wait to finish the season and re-assess everything."
Barca are second in LaLiga through 36 matches, a point behind Madrid – who can restore their four-point advantage with victory over Getafe on Monday.
Quique Setien's Barca are back in action for their penultimate league clash against Osasuna on Thursday.