By Tom DiChristopher, CNBC

Greece and its European creditors will not come to a comprehensive agreement by next week as had been expected, the head of the Eurogroup Working Group said Tuesday. However, Thomas Wieser is confident a deal will get done before a true crisis or bankruptcy ensues.

“We will get a deal,” Wieser said on CNBC’s “Squawk Box.”

“I think all of the polls show in Greece, the Greek population is firmly convinced its future is in euro. It has given a mandate, which is quite clear it seems to me and it seems to the Greek politicians, [to] do whatever it takes to come to a conclusion with the creditors.”

On Monday, members of the Eurogroup had hoped they would be able to signal that an agreement was in sight, but representatives for European finance ministers in Brussels are still battling over fiscal and value-added-tax issues and labor market reforms, Wieser said. The current funding program for Greece will last until the end of next month.

Greece, which is running out of cash, told its euro zone partners in February that by the end of April it would agree with creditors on a comprehensive list of reforms to get the remaining 7.2 billion euros from its bailout.

The leftist-led government in Athens remains locked in a standoff with its creditors—the euro zone and the International Monetary Fund—over the reforms.

Failure to unlock more funds would trigger a default, and possibly Greece’s departure from the euro zone.

While a Greek exit would have been “a real catastrophe” three years ago, Wieser said, today Europe is well insulated, but the outcome would still be negative.

“There’s quantitative easing of the ECB. We’ve got a $500 billion fund to take care of that. It would be very, very undesirable, bad for Greece, not good for Europe, not good for the world, so we’re fighting on,” he said.