Maronite Cardinal Nasrallah Sfeir (search), a strong critic of Syria's control in Lebanon who left Monday for a meeting with President Bush, has emerged as a key opposition figure whose influence cuts across sectarian lines in this religiously diverse nation.

The soft-spoken 84-year-old patriarch, head of the 900,000-member Maronite Catholic Church (search), began criticizing Syrian interference in Lebanese affairs when few dared challenge the authority of the pro-Syria government and its Syrian backers.

His first major salvo came in September, months before Lebanon was thrust into the spotlight with the Feb. 14 assassination of former Premier Rafik Hariri (search), a killing that has triggered mass street demonstrations demanding that Syria get out of Lebanon.

Syria "gives orders, appoints leaders, organizes parliamentary and other elections, brings in whoever it wants and drops whoever it wants, interferes in all aspects of life in the administration, the judiciary, the economy and particularly the politics, through its representative here and his aides," Sfeir complained in September.

He was protesting Syria's role in the passage of a constitutional amendment that led to the extending of the term of Lebanon's pro-Damascus president, Emile Lahoud (search).

Sfeir's bold broadside, and his campaign for Christian-Muslim harmony, won wide respect among Lebanon's Muslim majority, and all the country's political factions have courted him at his seat in Bkirki, on a mountain hugging the Mediterranean shore.

After meeting with the cardinal in January, Hariri, a Sunni Muslim, told reporters that "we always consider him a national authority."

As Sfeir left for a Wednesday meeting at the White House, hundreds of thousands of protesters jammed Beirut's streets to protest Syrian dominance on the one-month anniversary of Hariri's killing. The crowds forced Sfeir to be flown by helicopter from Bkirki to the airport.

The invitation to Washington followed Sfeir's meeting with French President Jacques Chirac (search), who has joined the Bush administration in demanding a thorough inquiry into Hariri's killing and pressing Syria to remove its troops and intelligence agents from Lebanon.

Despite his tough stance against Syrian interference in Lebanese affairs, the cardinal wants good relations between both countries.

"Syria is our neighbor and we are obliged to establish the best relations with it," he said recently. "But it must not interfere in internal Lebanese affairs. We are responsible for our fate in Lebanon."

Sfeir has been a strong advocate of Christian-Muslim coexistence in a country where Christians' political power dwindled over the decades as their majority evaporated and where sectarian divisions led to the devastating 1975-90 civil war.

He was instrumental in persuading hard-line Christians to approve the 1989 Arab-brokered Taif Accord (search), which ended the civil war. It also called for a gradual Syrian withdrawal from Lebanon and for political reforms that saw Christians lose control of the final say in government.

Sfeir also supports integrating Hezbollah (search), the Shiite Muslim militant movement that opposes Israel and is listed as a terrorist group by Washington, into Lebanon's political mainstream.