PHILADELPHIA -

Vice President Joe Biden can't stay away for long from the nation's birthplace.

Biden has visited Philadelphia for the second time in a week, speaking to a Greek Orthodox group at a downtown hotel.

Biden says he is optimistic the Greek economy is making a comeback.

He also says the exploration of natural gas in the region could help boost the recovery, and change the area's geopolitics.

The vice president drew a standing ovation when he spoke of the importance of religious freedom. He urged the reopening of a long-closed Orthodox seminary on the Turkish island of Halki.

But he says Greece must guarantee the rights of Muslims in return.

Biden spoke to more than 1,000 people at the Greek Orthodox Archdiocese of America congress.

Days earlier, Biden took part in Fourth of July festivities at nearby Independence Hall.