Mercedes buy into a team that has the championship once compared to several times by McLaren
"We are talking (with Button) and that's why we cannot announce the driver line-up," said Haug on Monday. "We have to accept that speculation takes place, but that's the name of the game."
But he added: "This will be an international team - Mercedes-Benz is a global player.
"We definitely do not want to have a pure German team. It's an international team and we want to have the best drivers in the car."
Daimler chairman Dieter Zetsche, whose company owns Mercedes, echoed Haug's thoughts.
"What we would like to see is the best drivers in the two seats," he said. "We certainly would not be opposed if one of them was German but that is not a prerequisite."
Button, who won the drivers' title this year, has been trying to secure a pay-rise from his £3.5m salary but it seems Mercedes is not interested in granting his wish.
The 29-year-old Englishman visited McLaren with manager Richard Goddard on Friday, with Button now expected to join the Woking-based team for a salary around double what Brawn were offering.
Button's decision is understood not to be solely about money - sources say he considers McLaren might have a more competitive car than Brawn in 2010.
Finn Kimi Raikkonen, who has been forced to leave Ferrari to make way for Fernando Alonso, remains an outside possibility for the seat alongside 2008 world champion Hamilton.
Despite the takeover, both Haug and Zetsche indicated that there were unlikely to be wholesale changes, with Ross Brawn remaining as team principal.
They also said Brawn would have a key role to play in deciding the driver line-up for 2010 and beyond.
"Ross Brawn is the boss of the team and it would not be smart of us to dictate to him anything like a driver decision," said Zetsche.
Brawn and chief executive Nick Fry will retain a 24.9% shareholding in the team. The remaining 75.1% will be split between Mercedes, which will own 45.1% and Abu Dhabi company Aabar Investments, which will own 30%.
Brawn said: "Brawn GP has been through an incredible journey over the last 12 months.
"From fighting for our survival to forging a strong relationship with Mercedes-Benz High Performance Engines, winning both the constructors' and drivers' world championships, and now accepting Daimler and Aabar's offer to buy our team, which will secure its future."
As part of a deal that will see the McLaren Group buy back Mercedes's 40% shareholding by 2011, the German company will continue to supply free engines and sponsorship to the team for at least the next six years.
The team's official name will remain Vodafone McLaren Mercedes.
McLaren chairman Ron Dennis described the deal as "a win-win situation, both for McLaren and Daimler".
McLaren and Mercedes said one of the reasons for them to split was because of McLaren's road-car building ambitions.
McLaren is launching a high-performance sports car called the MP4-12C in 2011.
Dennis said: "I've often stated that it's my belief that, in order to survive and thrive in 21st Century Formula 1, a team must become much more than merely a team.
"That being the case, in order to develop and sustain the revenue streams required to compete and win grands prix and world championships, companies that run Formula 1 teams must broaden the scope of their commercial activities.
"In the MP4-12C, which will be introduced to market in 2011, we have a car that has inherited the genes of the iconic McLaren F1 of 1994 and has already been the subject of much global media acclaim."
BBC SPORTS REPORT.