The Gunners have already signed defender Gabriel from Lille for £24m this summer, while Willian arrived from Chelsea on a free transfer.
However, manager Mikel Arteta has been keen to bolster his central midfield options before the window closes, with Arsenal continually linked with Partey as well as Houssem Aouar of Lyon.
On Sunday, Aouar confirmed he would not be leaving his current club, which means Arsenal have turned their full attention to Partey.
Arsenal and Atletico have previously been in negotiations for the Ghanian only for them to fail to come to an agreement, with the Spanish side insisting he would only be sold if his release clause was met.
Now, the release clause has been triggered, according to Goal.com, with Arsenal ready to pay £45m.
Following Arsenal's narrow victory against Sheffield Utd on Sunday, Arteta was asked about any potential recruits and he said he and the club would do their upmost to improve the squad on deadline day.
“What I can guarantee is that we are doing our maximum for that to happen, whether we are going to achieve it or not, I don’t know,” he said.
Partey currently holds a 85 FC Rating for his performances for Atletico. In the 2019/20 campaign, he made 35 appearances in La Liga for Los Colchoneros.