"I'm not hiding any secret about the Saudi position. We were reluctant until today. And if not for the Arab consensus we felt today, we would not have decided to go," al-Faisal said.
"But the kingdom would never stand against an Arab consensus, as long as the Arab position has agreed on attending, the kingdom will walk along with its brothers in one line."
Participation by al-Faisal was a key goal of the United States to show strong Arab support for the conference in Annapolis.
However, al-Faisal insisted that he would not allow "theatrics" like handshakes with Israeli officials, saying the gathering must make serious progress.
Until Friday, Saudi Arabia, which has no diplomatic relations with Israel, was reluctant and wanted assurance that Israel would negotiate the most difficult issues of the Israeli-Palestinian conflict - namely final borders of a Palestinian state, the status of Jerusalem and the fate of Palestinian refugees.
Walid Moallem, the Syrian foreign minister, has also conditionally agreed to attend the Annapolis conference.
The Arab ministers at the Cairo meeting have sent a letter to the United States asking it to "explicitly" include the issue of the Israeli-occupied Golan Heights on the agenda for the talks on Tueday.
Moallem said : "US Secretary of State Condoleezza Rice has promised a positive response to the request and if we receive a formal positive response, Syria will attend," Moallem told a news conference in Cairo.
Bashar al-Assad, the Syrian preisdent, has said that Damascus will not attend unless the status of the Golan Heights, the strategic plateau which Israel has occupied since 1967, is discussed.
Clayton Swisher, Al Jazeera's Middle East analyst, said Syria's participation will symbolise the importance of Hamas' involvement in resolving the Israeli-Palestinian conflict.
He said: "It brings back memories of the 1991 Madrid conference when the PLO [Palestinian Liberation Organisation] wasn't allowed to attend the conference but other countries were allowed to represent the group, namely through Jordan."
Meanwhile, Ehud Olmert, the Israeli prime minister, has praised the Arab peace plan and said negotiations launched at Annapolis will address the core issues.
He also said a final deal could be reached in 2008.
But Israel is resisting putting those commitments on paper in a final statement due to be announced at Annapolis.
In a draft of the joint statement, published on Thursday in the Israeli daily Haaretz, Israel's proposals make no mention of the main issues and avoid any talk of a timetable for negotiations.
The draft is said to reflect wide differences with the Palestinian proposals.