Jim McCaughan, chief executive of Principal Global Investors, said there was still a risk of Greece ultimately having to leave the euro zone. Greece and Germany remain divided over how to reduce the former's debt pile, he told CNBC, which stood at 176 percent of GDP in 2014, according to the European Commission.
"They haven't solved the fundamental impasse which is that the Germans are saying the debts must be paid and the Greeks are saying, basically, we won't pay them," McCaughan said.
"Isn't that a fundamental problem that will almost certainly cause a break (from the euro zone)?"
Although concerns over a Greek exit from the euro zone, nicknamed a "Grexit," have been persistent since the new Greek government came to power, Annenkov was sanguine, saying: "I think there is strong underlying force in keeping Europe together."
Despite efforts to keep the single currency area intact, Greece is under pressure to reform and conform to its lenders' expectations. The EU's financial affairs chief, Pierre Moscovici, said Monday that reaching a political deal for Greece at the EU summit this week depended on whether the country's government committed to undertaking reforms, Reuters reported.
"I think any kind of deal...relies on strong commitments of the Greek government," the European Commissioner for Economic and Financial Affairs said at an event in Berlin.
"Commitments to reform, commitments to do what is in the common agreement that we signed on February 20," he added, referring to the date when Athens was granted an extension to its bailout.