BERLIN (Reuters) - Britain must tell the European Union what it wants from an agreement on its exit from the bloc, Germany's Europe minister said on Wednesday after London's parliament rejected a negotiated withdrawal agreement for the second time.

"We are at the very limits of what's bearable," Michael Roth told Deutschlandfunk radio. "We have already changed the exit agreement once to suit Britain... We are open and prepared to talk but we aren't getting any clear views from Britain on what they want, only what they don't want."

A postponement of the currently agreed March 29 exit day was possible he added, but if it lasted beyond the beginning of June, then Britain would have to take part in scheduled European Parliament elections.

(Writing by Thomas Escritt; Editing by Riham Alkousaa)