LONDON (REUTERS) - Britain needs the European Union to agree to amend its founding treaties as part of its renegotiation drive, British Foreign Secretary Philip Hammond said on Thursday, saying London had to get a substantive deal to persuade voters to stay in the bloc.

"If our partners do not agree with us, do not work with us to deliver that package then we rule nothing out," Hammond told BBC radio. "The advice we're getting is that we will need Treaty change," he said.

Hammond spoke as Prime Minister David Cameron prepared to embark on a two-day tour of European capitals to try to charm other EU leaders into backing his reform plan.

He has pledged to reshape Britain's EU ties before giving voters an in-out EU membership referendum by the end of 2017.