Enke was selected over Werder Bremen's Tim Wiese to play against Liechtenstein in Leipzig on Saturday and Wales in Cardiff on April 1.
Bayer Leverkusen's Rene Adler, in goal for the last few internationals, sustained an elbow injury and was ruled out.
"There is no decision for a permanent number one yet," Koepke told reporters.
"We have very good keepers and we cannot answer this question yet. Once we decide we will announce it and move forward with that decision," said Koepke, a former Germany international keeper.
Koepke said a decision would not come very soon, with an announcement sometime before the World Cup in South Africa.
Germany top European Group 4 with 10 points from four matches. Russia are second on six points from three games.
Since the departure of Jens Lehmann and his long-time predecessor Oliver Kahn, there has not been a first choice goalkeeper, with the three candidates having a combined total of only nine international caps.
Koepke ruled out a return by Lehmann after a media report on Friday suggested the VfB Stuttgart keeper was interested in playing in another World Cup.
"I read it as well but we have no thoughts about this and will make no thoughts either. It would be the wrong signal to the young keepers."
Enke, whose club languish in 13th place in the Bundesliga with no chance of giving the keeper any European competition experience, said he was up to the challenge.
"This competition, I accept it," said the 31-year-old.
"I have seen the arguments against me but they have nothing to do with my personal performance. It's always the club."
"The (Germany) coaches here say clearly that I don't need to change. So I don't feel pressured. I have another year on my contract and we will see."
