Speaking at a news conference with Palestinian chief negotiator Ahmed Qureia in the West Bank city of Ramallah, Solana said a positive outcome to the conference in Annapolis, Maryland, expected to convene this month, is vital.
"It has to be a success," Solana said. "I don't want to say that it's not difficult, it will be difficult, but I think it's doable, it is possible."
While the conference is dedicated to the Israeli-Palestinian issue, U.S. officials have said that Washington will invite 12 Arab nations to attend, to demonstrate broader regional support for the initiative.
"Syria will be invited, Egypt will be invited," Solana said. "We hope that that all those who are invited will come."
Syria, technically at war with neighboring Israel, says it will not come unless the future of the Golan Heights - a strategic plateau Israel captured from Syria in the 1967 Mideast war - is on the agenda. Israel says Syria is welcome to come to the conference, but it is not the proper venue for talks on the Golan.
However, an Israeli newspaper reported Tuesday that Israel Prime Minister Ehud Olmert had renewed secret peace overtures to Syrian President Bashar Assad, and told him Israel could return the Golan if Damascus severs its ties with Iran and militant groups.
Egypt, with Jordan one of only two Arab states to have made formal peace with Israel, has also been expressing reservations about taking part, saying it is not clear that it will generate clear steps to ending the Palestinian-Israeli conflict.
Solana, on a Mideast tour to try to close gaps ahead of the Annapolis conference, met in Cairo Monday with Egyptian President Hosni Mubarak and Foreign Minister Ahmed Aboul Gheit and on Wednesday will meet in Jerusalem with Olmert and Foreign Minister Tzipi Livni.