FRANKFURT (Reuters) - General Motors <GM.N> reaffirmed its commitment to its ailing European arm Opel, rejecting on Friday speculation it might be interested in disposing of the loss-making brand to rival Fiat <FIA.MI>.

"Opel is not for sale. GM fully stands behind Opel," GM Vice Chairman Stephen Girsky said in a brief statement sent by email.

Earlier on Friday, Italian daily Il Sole-24 Ore wrote in an unsourced report that Fiat <FIA.MI> Chief Executive Sergio Marchionne is ready to buy Opel if GM's alliance with France's Peugeot <PEUP.PA> dissolves.

"Opel is a fully integrated part of GM's global footprint and vital for GM's future success in Europe. The GM-PSA alliance is fully on track," Girsky said in the statement.

Fiat had expressed interest in acquiring Opel -- known as Vauxhall in the UK -- in 2009, only to see a consortium around Canada's Magna <MG.TO> be awarded exclusivity in negotiations with GM that later collapsed.

(Reporting By Christiaan Hetzner)