SARAJEVO (Reuters) - Bosnia must start making concrete reforms if it wants to join the European Union, or the window to becoming a member could close, the bloc’s enlargement chief said on Monday.

The European Union accepted Bosnia’s application 15 months ago - but Johannes Hahn said the Balkan nation had not made any of the reforms or changes agreed with the bloc and international creditors.

“So far nothing has been delivered. We now expect very concrete results,” Hahn said after meeting political leaders.

Bosnia’s prime minister, Denis Zvizdic, said he hoped the leaders would reach a compromise on outstanding issues by later this month or early January.

The ethnically divided country has so far not managed to respond to the initial EU questionnaire on its readiness to join the bloc.

Political bickering has held up a law raising excise tax on fuel, required to unlock external financing for infrastructure projects. There has also been no sign of development and energy and agriculture sector strategies demanded by the bloc.

“There are a lot of issues in the pipeline but I would like to have them through the pipeline,” said Hahn.

“It is absolutely high time now to deliver on what has been agreed, otherwise, the window can be closed again and this is not something we all would like to see,” he told a news conference.

Hahn urged government and opposition leaders to stop appealing to ethnic nationalism, and said the EU would be looking for evidence of European values, including a respect for court rulings.

“Without that understanding one cannot make any progress,” he said.