Tusk's draft negotiating guidelines say that other 27 countries are ready for a transitional deal after Britain's exit in 2019.
But the EU said it would not allow the United Kingdom to pay for access to the European single market for key economic sectors like financial services and auto makers, raising the stakes for securing a free trade deal.
Spain must have a say over whether any deal after Brexit applies to the British territory of Gibraltar, over which London and Madrid have rowed for 300 years, the European Union guidelines said.
President of the European Council Donald Tusk confirmed delivery of the letter on social media.
However, her hopes to discuss separation terms and a "bold and ambitious" free trade agreement at the same time have been knocked back by German chancellor Angela Merkel and French president Francois Hollande.
He said: "A big mistake that we could make from both sides is to start with launching threats to each other".
Unless the United Kingdom government manages to negotiate a new bilateral flights agreement with the EU soon, United Kingdom carriers will have no right to fly to Europe and European airlines won't be allowed to fly to the UK.
The EU was open to talks if quick progress is made on key parts of the divorce proceedings - a move that grants some of the wishes of PM May.
Why Are Flags At Half-Mast Today? Astronaut John Glenn Honored
When he was 77 and completing his fourth term in 1998, he returned to space as a crew member aboard the space shuttle Discovery. Flags will be flown at half-staff across the state on Thursday in honor of OH senator and legendary NASA astronaut John Glenn .
Legally, a trade deal can not be signed until Britain has left and many on both sides believe that, going by typical times to negotiate such accords, it will take several years beyond 2019 before one is in place.
It marks the start of complex and contentious negotiations that put the United Kingdom on course to break its ties with Brussels by the end of March 2019.
Several decades of joint work are at stake and it is a common interest that relations should remain good after Britain's exit from the bloc, he said, adding that for this reason it was important that negotiations should be pragmatic.
European officials suggested enough progress could be made on the divorce arrangements by the end of the year to begin trade talks, although EU leaders will have the final say. "But paradoxically there is something positive in Brexit", Tusk added.
European Council President Donald Tusk on Friday set out the fundamental guidelines for the two-year Brexit negotiations.
But she also reiterated her warning that failure to reach a trade deal would hamper security ties.
What it does want is to agree the "methodology" of how to work out the "Brexit bill", taking into account Britain's share of European Union assets and liabilities. The outpost at the southern point of the Iberian Peninsula has a population of 32,000 and about 96 per cent of its residents voted to remain in the European Union past year.
With a potential row now building up over Britain's so-called "exit bill", estimated to be as much as 60 billion euros ($64 billion, £52 billion), Gabriel also reminded Britain that it is obliged to meet its financial commitments to the EU.