* Commission offers common funds for joint military projects
* Revitalised defence push comes after Brexit, Trump, Crimea
STRASBOURG, June 13 (Reuters) - The European Union's executive proposed on Wednesday a 13 billion euro ($15.3 billion) defence and security fund for the first time to help build up depleted militaries that are heavily reliant on the United States.
The fund for the 2021-2027 period aims to support the European Union's efforts to integrate militaries - plans that were long blocked by Britain because it feared the creation of an EU army - and defend against Islamic militants and a resurgent Russia.
"It shows we are serious," EU Industry Commissioner Elzbieta Bienkowska told a news conference at the European Parliament, which along with EU governments must agree to the plan.
Separately, the Commission also proposed a 10.5 billion euro "European Peace Facility" to fund EU military missions abroad.
With Britain leaving the bloc next year, France and Germany see military cooperation as a way to show EU citizens that the bloc is still relevant, while U.S. President Donald Trump's sharp criticism of allies has also lent urgency.
Failings in Europe's bombing campaign in Libya in 2011, when the United States had to step in with refuelling planes, and Russia's 2014 annexation of Crimea have reignited calls for greater EU defence cooperation that date back to the 1950s but have made little progress.
The money for the EU fund will come from the bloc's common budget, split between 4 billion euros for research and 9 billion euros for developing prototypes that would be the basis for new hi-tech uniforms, drones, radars, ships and aircraft.
Under the plan, the fund would cover 20 percent of the military development costs, meaning EU governments would also put forward money to raise the overall size of the fund.
"This is just the start," Commission Vice President Jyrki Katainen said. "One can wonder where we could be in 10 years."
Any assets such as drones or military transports would be owned by EU governments and would be at the disposal of both the European Union and the U.S.-led NATO alliance, officials said.
To be able to qualify, projects must involve at least three companies from three EU countries, Bienkowska said, because the Commission is trying to overcome duplication and wasted funds. Until now, EU governments have awarded most defence contracts to their own firms rather than use European consortiums.
While Britain long resisted such proposals and preferred to rely on NATO for EU defence, British officials have approached the European Commission in recent months to seek involvement of Britain defence contractors in lucrative EU projects.
Britain is still negotiating the terms of its EU divorce but at this stage however, Bienkowska was adamant: "The fund is open for companies based in the EU." ($1 = 0.8512 euros) (Reporting by Gilbert Reilhac, writing by Robin Emmott; Editing by Toby Chopra)