Pope John Paul II ended his 96th foreign tour with the Vatican suggesting he may not make many more. At home, however, he still has plenty on his plate, including a meeting this week with President Bush.

Vatican spokesman Joaquin Navarro-Valls said there was an open agenda for Tuesday's meeting with Bush at the Vatican, although he suggested the Middle East and problems of the Roman Catholic Church in Russia may be discussed.

When the two met last July at the pope's summer residence, the top issue was stem cell research. The pope urged Bush to reject research on human embryos — one of many voices he heard before announcing support for federal funding for limited medical research on existing lines of embryonic cells.

John Paul goes into Tuesday's meeting after a trying five-day trip to Azerbaijan and Bulgaria, which concluded Sunday with Navarro-Valls suggesting the pope may have to cut back on future trips.

John Paul will go to Toronto in July to mark the Roman Catholic Church's World Youth Day, Navarro-Valls said. But he suggested the Vatican was carefully evaluating whether the ailing pope could handle stops in Guatemala and Mexico on the proposed 11-day trip.

``Toronto is clear. For the others, we shall see,'' Navarro-Valls told reporters in Bulgaria. ``No decision has been made yet. Everything that has been confirmed is confirmed.''

But he added: ``Something that has been confirmed can be unconfirmed.''

Throughout his 24-year papacy, the only trips postponed because of John Paul's health were a 1994 visit to New York after the pontiff broke his leg and a trip to Armenia in 1999 after he came down with the flu.

Despite persistent questions about the pope's health and flagging strength, the Vatican had insisted as recently as Saturday that no changes would be made to his travel schedule. Underscoring how sensitive the issue is, Navarro-Valls issued a statement later Sunday stressing that no decision on the Mexico and Guatemala visits had been made.

Winding up a taxing four-day Bulgaria trip Sunday with an outdoor Mass in the southern city of Plovdiv, the pope sat slumped in a white chair on the altar, looking feeble. His hands trembled and his voice was heavily slurred, symptoms of Parkinson's disease.

Although he has difficulty walking and has been wheeled around on a special platform, Navarro-Valls denied there were any plans to use a wheelchair on future trips.

As he did throughout the Bulgarian visit and in Azerbaijan, the pope read only a portion of his homily, turning it over to a priest to finish.

But the pope's final event before returning to Rome — a meeting with Catholic youths at a church in Plovdiv — appeared to energize him, as his encounters with young people often do. An alert John Paul waved repeatedly and reached out to touch some of the several hundred wildly cheering and weeping youths.

``I'm glad to meet young people at the end of my visit to Bulgaria. Tomorrow belongs to you,'' the pope said in Polish. He added: ``Probably it's my last trip to Bulgaria.''

Showing his spirit despite his infirmities, the pope invited the journalists traveling with him to come up to the front of the plane, one by one, and pose with him for photographs before it took off.

Back in Rome, the pope again used a mechanical lift instead of stairs to get off the plane. He used the lift for the first time when he left Rome on Wednesday.

About 20,000 people attended the Mass on Plovdiv's main square, where security was particularly heavy. Sharpshooters stood on rooftops and windows overlooking the square were covered.

Two Orthodox church officials who had accepted the pope's invitation stood beside him, an encouraging sign for the Vatican, which has been seeking closer contacts as part of efforts to heal a millennium-old rift between Catholics and Orthodox Christian believers. Disputes between the two faiths have thwarted the pope's longtime hopes of visiting Russia.

The pope beatified three Catholic priests killed by Bulgaria's former communist regime, finding bonds with Orthodox Christians in their joint suffering during the Cold War.