ATHENS, July 11 (Reuters) - Greek Prime Minister Alexis Tsipras claimed a strong mandate to complete negotiations with international creditors after winning the backing of parliament over a painful new package of reform measures.

In a statement issued after the vote in parliament, which the government won with the help of pro-European opposition parties, Tsipras said he had a "strong mandate to complete the negotiations to reach an economically viable and socially fair agreement".

He made no mention of rebels within his own leftwing Syriza party who withheld support for the measures but said his focus was on completing the negotiations.

"The priority now is to have a positive outcome to the negotiations. Everything else in its own time," he said.

(Reporting by James Mackenzie; editing by Costas Pitas)