European Commission chief Jean-Claude Juncker refused Tuesday to entertain the idea of a British exit from the European Union, saying there is no "plan B" ahead of talks with British Prime Minister David Cameron.
Juncker, head of the EU executive, said he expected Britain to stay in 28-nation bloc as "a constructive and active member."
"If I would say now that we have a plan B, this would indicate a kind of willingness of the commission to envisage seriously that Britain could leave the European Union," Juncker told a debate at the European Parliament in Brussels.
"So I am not entering into the details of a plan B, because we don't have a plan B, we have a plan A. Britain will stay in the European Union as a constructive and active member of the Union," he said.
Juncker said the Commission and European Council President Donald Tusk were working on a number of proposals for a key EU leaders summit in Brussels on Thursday and Friday.
It remains to be decided whether the proposals are "seen as being fair for Britain and are seen as being fair for other member states," he added.
Cameron has four key demands, the most important being restrictions over four years on welfare payments to EU citizens working in Britain.
He also wants non-euro countries such as Britain to have safeguards against closer integration of the single currency area, an opt-out from ever closer union and strengthened national sovereignty.
Earlier Tuesday, Cameron met European Parliament head Martin Schulz, aiming to win support for the reforms he wants if he is to campaign to keep Britain in the bloc