The Gunners have agreed a fixed fee of 55 million pounds for the Swedish forward, but negotiations are still ongoing regarding the proposed 10 million euros in add-ons.
Manager Mikel Arteta, currently with the squad on their pre-season tour of Singapore and Hong Kong, has declined to publicly comment on the situation, when asked whether Gyokeres would be signed in time for the start of the new season.
The deal, although advanced, has yet to be completed as Sporting hold firm on their conditions for the add-ons.
"I cannot comment on any player who is not part of our group yet," said Arteta.
"When we have something concrete to offer in any case to any player we will do that.
"I'm very pleased, that's all I'll say.
"There are a lot of parties and things that we have to bear in mind to get a player over the line and here. I'm very hopeful that we are going to do it very soon.
"There's still a long time in the window and we are seeking still, in terms of numbers, we are short and we have to improve the depth and quality of the squad.
"We are constantly looking in the market. Until that happens, focus on the players we have and focus on them and I'm very pleased with what I have seen in the last 10-15 days."
Arsenal, under the guidance of new sporting director Andrea Berta, are pushing to finalise terms swiftly with the Premier League opener fast approaching.
Gyokeres is not the only name on Arsenal's radar. Talks are progressing with Valencia over a 13-million-pound move for defender Cristhian Mosquera, in what would be another addition to Berta's growing list of summer acquisitions.
So far, Arsenal have secured the signings of goalkeeper Kepa Arrizabalaga, midfielders Martin Zubimendi and Christian Norgaard, and winger Noni Madueke as part of their summer rebuild.
Arsenal defender Gabriel Magalhaes says the club is ready to turn near-misses into silverware this season, declaring, “We've let a couple of titles slip, but this year will be different”.
Noni Madueke will not feature in Arsenal's upcoming pre-season tour of Asia, following his recent high-profile switch from Chelsea in a deal worth up to 52 million pounds.
Arsenal are racing against time to secure the signature of Sporting CP's prolific striker Viktor Gyokeres, but unresolved details have left the transfer hanging in the balance.
Arsenal have confirmed the signing of England international Noni Madueke from Chelsea in a deal worth an initial 48.5 million pounds.
