Gabon international Aubameyang, 31, has been Arsenal's top scorer in each of the past two seasons and has only one year left on his current contract.
"I keep being positive, we have had some really good talks with him and his agent," Arteta told reporters in a virtual news conference ahead of Saturday's Community Shield match against Liverpool at Wembley (stream LIVE on ESPN+ at 11:30 a.m. ET in the U.S.).
"I'm confident we will find an agreement soon. He should be very happy that he will be staying at the club for a long time."
Having been named captain for the second half of the season, the Wembley triumph delivered the striker's first trophy with the club since he joined from Borussia Dortmund in January 2018.
"We're trying to finalise the deal," Arteta said. "Everything is ok only when both parties agree. We're pretty positive.
"He's a player we followed and were determined that he was the right profile for us to improve our squad. When we get it [over the line] we'll be very pleased."
"He was pretty clear with me that his intention was to remain with us but obviously Real Madrid is involved," Arteta said. "I don't know yet what they want to do with the player.
"But he's a player that we are interested in because we really saw, in the last few months of the season, what he is capable of bringing to us."