Swiss President Simonetta Sommaruga is turning 60 on May 14 and is planning a party with a difference by inviting along all Swiss citizens who share her birthday.

There were 94,372 births in Switzerland in 1960 - the year Sommaruga was born - meaning that the average maximum number of invitees would be around 258.

Sommaruga is not taking any chances with potential gatecrashers and is asking prospective celebrants to submit a copy of their passport through the presidency website.

"I would be delighted to receive your registration for my birthday party," Sommaruga wrote on Twitter on Thursday.

She is also keeping the location secret and said only that it would be "in the Bern area" - the Swiss capital.

The Swiss presidency is a largely ceremonial role that rotates annually between leading political parties.

Sommaruga, a Socialist Party member who already served as president in 2015, took up her post on January 1 and delivered her New Year's address from her local bakery.