VATICAN CITY — Pope Benedict XVI on Monday sang along to the anthem of his native Bavaria in Germany to celebrate his 85th birthday, which makes him the oldest pope since Leo XIII who died in 1903 aged 93.

The pope began his birthday with mass in the frescoed Pauline Chapel in the Vatican's Apostolic Palace along with his 88-year-old brother Georg Ratzinger, himself a bishop and the pope's closest surviving relative.

"I am facing the final leg of my life's path and I don't know what's ahead," an emotional Benedict said in his homily.

He was then welcomed in the Vatican's ornate Clementine Hall by about 150 Bavarians, including Bavaria's state governor Horst Seehofer, and was serenaded by dancing children in traditional costume.

Several German Church leaders including Reinhard Marx, archbishop of Munich, and Robert Zoellitsch, the head of the German bishops' conference, as well as a Protestant Bavarian bishop and the leader of the regional Jewish community, Charlotte Knobloch, also attended.

The friendship with Jewish officials "has brought the Jewish people closer to me", said Benedict.

Italian President Giorgio Napolitano, an 86-year-old former communist, and Prime Minister Mario Monti, were among those who sent congratulations to the pope.

The smiling head of the Roman Catholic Church was given several presents, including a crucifix and a traditional Bavarian Easter basket. He told those gathered to celebrate his birthday that they represented "every stage" of his life.

The pope -- who has recently appeared tired and occasionally uses a cane to walk -- told pilgrims on Sunday: "I ask you to pray for me, that the Lord may give me the strength to fulfil the mission that he has given me."

Vatican spokesman Federico Lombardi said Benedict, who plans to visit Lebanon in September, was tired like other men his age, but "lucid".

In interviews in 2010, Benedict raised the possibility that he could resign if he was no longer able to carry out his duties -- mindful perhaps of the long debilitating illness of his predecessor John Paul II, who died aged 84.

The German pope had told his closest aides that he wanted "no major celebrations" and prefered "a family celebration", the pope's personal secretary Georg Gaenswein said in an interview with the Italian weekly Gente.

On Thursday he also celebrates the seventh anniversary of his election.