Pope Francis could become the first pontiff ever to address Congress after being offered a historic invitation by US House leaders on Thursday. House Speaker John Boehner sent a formal, open invitation to the pontiff, who on Thursday marked the first anniversary of his election to lead the world's 1.2 billion Catholics. Boehner's office said the Vatican had yet to respond to the invite. Boehner in a statement lauded Francis's popular message of mercy and serving the poor and how it transcended religious and cultural differences. "Pope Francis has inspired millions of Americans with his pastoral manner and servant leadership, challenging all people to lead lives of mercy, forgiveness, solidarity, and humble service," Boehner said in a statement. "His tireless call for the protection of the most vulnerable among us -? the ailing, the disadvantaged, the unemployed, the impoverished, the unborn -? has awakened hearts on every continent." No date was mentioned in the invitation, but reports have said the pope hopes to visit the United States next year to attend a global conference on families in Philadelphia in September. Top House Democrat Nancy Pelosi, who attended Francis's inauguration last year at the Vatican, said she was pleased that the pope would be able to bring his message directly to Americans. "Pope Francis has lived his values and upheld his promise to be a moral force, to protect the poor and the needy, to serve as a champion of the less fortunate, and to promote love and understanding among faiths and nations," said Pelosi, who like Boehner, is Catholic.