ATHENS (Reuters) - Greece's main opposition and ruling parties issued a joint declaration on Monday backing the government's efforts to clinch a new aid deal, a move by Prime Minister Alexis Tsipras to cement broad support after a resounding referendum win.

"The government is taking the responsibility to continue the talks, and each political leader will contribute respectively within the framework of his/her institutional and political role," said the statement, issued by the presidency.

The leaders said they were seeking a deal with European and IMF creditors that ensure adequate funding, credible reforms, a growth plan and the commitment to start discussions on the sustainability of Greece's massive debt.

Their immediate priority was to get banks open again, they said.

(Reporting by Renee Maltezou; Writing by Matt Robinson)