Cameron unsure of Britain's EU membership if Juncker elected Commission chief

British Prime Minister David Cameron said he can’t promise his country’s commitment to the EU if its leaders choose Jean-Claude Juncker as European Commission head, given their differences on Britain’s future in the bloc, Germany’s Spiegel reported.

Juncker was nominated as a candidate by the European People's Party, which received the largest number of seats in last week's European Parliament elections. The European Commission chief will first be elected by EU leaders, after which the individual must be given a green light from the assembly.

While speaking on the sidelines of Brussel's summit on Tuesday, Cameron made clear that he would no longer be able to guarantee the UK would stay within the EU if Juncker was elected, according to a pre-publication copy of Spiegel's article obtained by Reuters.

The article interprets Cameron’s message as saying that if Juncker is chosen, the UK would have to go through with the referendum on the future of EU membership, which would most likely result in British citizens choosing to opt out of the EU.

Cameron criticized Juncker for being too federalist and said "a face from the '80s can't solve the problems of the next five years.”

Earlier, Cameron made clear that he would be renegotiating the terms of Britain's EU membership and proposed to hold a membership referendum by the end of 2017 if elected.

The Conservative leader is not the only person opposing Juncker's candidacy.

French President Francois Hollande wants to see a Frenchman as the head of Commission, Germany's Bild am Sonnta newspaper reported, citing a source. Hollande allegedly proposed his own candidate to German Chancellor Angela Merkel – former French finance minister Pierre Moscovici.

Despite objections from powerful EU leaders, Juncker remains positive about his chances of becoming the next European Commission head, stating that he is “optimistic about being chosen as the next Commission president by mid-July.”

Juncker called on the majority of EU leaders not to allow themselves to be pressured by the minority when making their choice.

“Europe must not allow itself to be blackmailed,” Juncker said, while pointing out that he has large support from Christian Democratic and Socialist leaders in the European Council.

European Energy Commissioner Guenther Oettinger said the decision will likely be made before the summer recess. "Given that the EPP, with Jean-Claude Juncker, has a leading margin of more than 20 seats in the EU Parliament, the Council should nominate him," Bild am Sonnta quoted him as saying.

In the event that a decision is not made before summer break, EU politics could come to a standstill, Oettinger stated.