"There will be no single market a la carte," Tusk told a news conference in Brussels after the 27 leaders met without British Prime Minister David Cameron.
"Leaders made it crystal clear today that access to the single market requires acceptance of all four freedoms including freedom of movement," Tusk added.
The 27 EU leaders will also hold a summit -- without Britain -- in Bratislava on September 16 to discuss further the fallout from Britain's decision to leave the bloc, Tusk said.
"This was a first exchange so it is too early to draw conclusions. This is why we started a political reflection with 27 states and we'll meet on September 16 in Bratislava to continue our talks," Tusk said.
The former Polish premier stressed that negotiations on Britain's future relationship with the EU cannot start until it formally triggers the two-year process leading to a divorce.
Tusk meanwhile said at the "calm and serious" discussion -- the first EU talks without a British leader present for 40 years -- they agreed it was a "serious moment in our common history."
"One issue is clear from our debate. Leaders are absolutely determined to remain united," he added.
