"In a democracy, everybody is beatable," Gabriel said in an interview to be published in this Monday's edition of the mass-circulation daily "Bild."

"The SPD (Social Democrats) will nominate a candidate and fight for the chancellorship," Gabriel added.

Gabriel was reacting to comments made last month by Torsten Albig, the SPD premier of the northern state of Schleswig-Holstein. Albig told public broadcaster NDR that there was no real point in the SPD putting up a candidate to challenge Chancellor Angela Merkel, because it would be "stupid to think that we could win."

If the opinion polls are to be believed, a fortnight later, Albig may have an argument, with a survey conducted for "Bild" by the Emnid polling institute giving Merkel's Christian Democrats (CDU) 43 percent support among decided voters, with the Social Democrats trailing far behind at just 24 percent.

However, Gabriel told the paper that a lot could change between now and 2017, and pointed to what he said were his coalition partners' weaknesses when it came to serious political issues, including the "squabbling over Europe between Angela Merkel and (Finance Minister) Wofgang Schäuble."

'It can't get any better for Merkel'

In a separate interview with the DPA news agency, Gabriel's deputy as party chairman, Ralf Stegner, said he, too, believed the SPD would have a chance of knocking off Merkel, by the time the next general election rolls around.

"Ms. Merkel is at the height of her popularity; it can't get any better" for her, Stegner argued. He also pointed to discord within the CDU and its Bavaria-based sister party, the Christian Social Union, over Greece. Some 60 deputies from the block recently ignored the chancellor's wishes and voted against opening negotiations with Greece on a third bailout package. Five others abstained. Stegner describe the atmosphere in the conservative parliamentary group over the issue as being "ablaze."

Looking ahead to the next campaign, Gabriel also expressed openness to the idea of letting the general party membership elect the next chancellor candidate, something that the youth wing of the party has pushed for. At the same time, he pointed out that to do that, they would need "more than one candidate."

Gabriel, who is also vice chancellor under Merkel, declined to be drawn on whether he would be throwing his hat into the ring in 2017.

pfd/gsw (dpa, AFP)