"The newspaper also reports that the Government "[does] not rule out United Kingdom troops serving under European Union command structures or continuing to pay into the EU's foreign affairs or development budgets".
Juncker's annual address seeks to provide a broad reflection on the future path of the European Union, the need for which has been strengthened following the United Kingdom's exit from the 27-nation bloc.
But EU Commission president Jean-Claude Juncker said the UK's departure from the bloc was not the "be all and end all" for Brussels.
Juncker, a former prime minister of Luxembourg and long-time chairman of the euro zone finance ministers group, has sounded alarm at noisy disputes over European Union subsidies, civil liberties, fiscal policy and national sovereignty that are dividing northern and southern states, rich and poor, the west from the ex-communist east.
"Nonetheless we have to respect the will of the British people, but we will have to make progress, we will move on, because Brexit isn't everything - it's not the future of Europe".
"All of this leads me to believe: the wind is back in Europe's sails".
The head of the EU's powerful executive arm is not expected to dwell on Brexit but will say it is a "huge opportunity" that could end divisions among the remaining 27 members, European sources said. Cyprus and Malta are the only other two European Union member states whose goods feature in the top 15. "They belong where freedom of expression reigns", Juncker said.
According to the UK Secretary of State for Exiting the European Union David Davis, the parties have managed to achieve "concrete progress", while European Commission's chief negotiator Michel Barnier stated skepticism, saying there was no decisive progress on any of the principal subjects.
"We should also allow Croatia to become a full Schengen member once it meets all the criteria", he added.
Juncker furthermore backed French President Emmanuel Macron's call for a pan-European finance minister, a big step towards deeper integration of the eurozone, whose proponents want to see further united to tackle any future crisis.
To much applause from the European Parliament, he called on the Turkish government to stop attacking EU leaders and to "let our journalists go".
Turkey's own long-stalled membership bid was ruled out "for the forseeable future" as a result of President Recep Tayyip Erdogan's crackdown following a coup attempt a year ago, he said.