The European Union said Friday it will unveil plans for closer military cooperation after Britain's referendum on whether to the bloc, but denied they were secret proposals for an EU army.

EU foreign policy chief Federica Mogherini last year began drawing up a "global strategy" for foreign and security policy in the wake of a series of challenges including Ukraine, Syria and the migration crisis.

But Brussels rejected a report in Britain's The Times newspaper that said there were secret plans for creating an army across the 28-member bloc, a long-time fear of eurosceptics.

"There is absolutely no plan to set up an EU army with the global strategy. There is also no secret paper," an EU spokeswoman told AFP.

The spokeswoman said Mogherini's preparation of the strategy was "ongoing, in an open and transparent way and is done in consultation with member states and many other stakeholders", adding that there was also a website about the plans.

She said Mogherini will present the strategy to the European Council at a summit on June 28-29, the week after the so-called Brexit referendum on June 23.

The EU has long been trying to improve its cooperation on defence issues, with some countries including Germany and France having formed so-called "battlegroups" that are ready to be deployed in crisis zones.

An EU source added that "when it comes to security and defence policy, the European Council has expressed its wish to see a more effective policy".

But the source added that the strategy would be within the existing EU treaties, recognise the preferences of member states including Britain "and will in no way aim to set up an EU army".

A European diplomat said the plans were "approaching the final phase," adding: "We will see when exactly it will be presented, since there is a referendum which can have some influence on the exact moment."

The Times report was seized upon by campaigners pushing for Britain to leave the EU, but the British government dismissed it.

"The prime minister has repeatedly made clear that the UK will never be a part of an EU army," a Ministry of Defence spokesman said.

"We retain a veto on all defence matters in the EU and we will oppose any measures which would undermine member states' military forces."

But UK Independence Party (UKIP) leader Nigel Farage, who is pushing for Britain to leave the EU, hailed the report as proof that the "pro-EU establishment" was lying to the British public.

Farage said on Twitter: "Pro-EU establishment not telling the truth -- European Union pushing for a full EU army."