"It's never enough time to prepare a team in one week but this is an exceptional situation. Chelsea have good players and they should be in top form and that should make my job easier," he said.
Hiddink said he planned to attend Chelsea's FA Cup fifth round tie at Watford on Saturday.
Chelsea confirmed the appointment on their website: "Chelsea Football Club are delighted to confirm Guus Hiddink will become temporary coach until the end of the season. He is due to meet the players this week.
"The club would like to take this opportunity to thank the Russia Football Union for their understanding and cooperation."
The Dutchman said he intended to contact his predecessor at Chelsea, Luiz Felipe Scolari, to discuss the team. Scolari was sacked by the fourth-placed Premier League club on Monday.
"I haven't done it yet but I will call him in the next day or two," said Hiddink.
He added he had not signed a contract with Chelsea nor intended to.
"I don't have to sign one. It's not a question of money," said Hiddink who has a close friendship with billionaire Blues owner Roman Abramovich.
Hiddink revealed to Reuters on Tuesday that he would be taking charge on a temporary basis at Chelsea for three months until the end of the current season and planned to continue as Russia coach.
He said he would be flying to Amsterdam later on Wednesday before travelling on to London.
Asked on Wednesday if he intended to bring any assistants with him to Stamford Bridge, he replied: "Not at this time."
"I always want to see the situation in the team myself first before making any changes if they have to be made," he said.
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