Hiddink took temporary charge at Stamford Bridge in February on a contract due to expire at the end of next month.
"Guus Hiddink came here on a temporary basis two months ago and it is thanks to the Russian FA that he was able to come here; it is purely a temporary role," Buck said on the club's official website.
Hiddink has repeated more than once that he intends to return to the Russian side fulltime when his contract at Stamford Bridge ends. A number of top Russian internationals have said they would fear for the future of the national team if Hiddink were to leave.
"There has been a lot of speculation about him staying, particularly as he has been doing a great job. That will not be the case," Buck said.
Chelsea have been resurgent since the Dutchman's arrival following a difficult period under Brazilian coach Felipe Scolari, and talk of him staying on intensified after last week's 3-1 victory at Anfield in the first leg of their Champions' League quarterfinal with Liverpool.
Hiddink became the manager of the Russian national team in 2006 and immediately set about rebuilding a demoralized side that had not managed to get out of the group stages at a major tournament since the break up of the Soviet Union. The Dutch coach brought in a host of new, young players, and Russia were transformed into an attacking, adventurous side, subsequently making the semifinals of Euro 2008.
Since taking the reigns at Stamford Bridge he has overseen Russia's unconvincing wins over Azerbaijan and Liechtenstein in qualifying for the 2010 World Cup. The next qualifiers are in June.
Hiddink's contract with Russia runs through next year's tournament in South Africa.
