BEIRUT, JUNE 29 -- Syria has increased pressure on extremist Shiite Moslems to release foreign hostages by confining the allied Iranian Revolutionary Guards to their eastern Lebanon stronghold, Shiite sources said today.

The sources, who are close to the Syrian Army command in Lebanon, said about 3,000 guards in the Bekaa Valley have been barred from military roads that cross the Syria-Lebanon border. The sources said the guards are stopped at military checkpoints or border customs posts when they try to travel.

Syrian officers also canceled the Iranians' firearms permits as part of a campaign to get Iranian-backed militants to free American journalist Charles Glass, who was abducted June 17 while driving through the Shiite suburbs of south Beirut.

Glass is one of at least 24 foreigners, nine of them Americans, who are missing in Lebanon. Shiite extremists backed by the Iranian regime of Ayatollah Ruhollah Khomeini are believed to hold most of them.

Also missing is Anglican Church envoy Terry Waite, who vanished in Beirut on Jan. 20 while on a mission to try to free foreign hostages.

Syria is Lebanon's main power broker and keeps about 25,000 soldiers in the northern and eastern parts of the country, including the Bekaa Valley. The abduction of Glass has been seen as a serious challenge to the Syrians, who sent about 7,000 troops to Moslem west Beirut on Feb. 22 to curb militia lawlessness.

Iranian Revolutionary Guards came to Lebanon in 1982 to help the Syrians against Israel's invasion in June of that year. The guards have training camps in the Bekaa Valley and in the south Beirut slums and have built the fundamentalist Hezbollah, or Party of God, into one of Lebanon's most powerful militias.

Hezbollah is believed to be the umbrella group for factions that have claimed responsibility for most of the abductions of foreigners during the past two years. So far, the Syrian troops in Beirut's Moslem sector have stayed out of the Shiite slums, where Hezbollah has its headquarters and most of the missing foreigners are believed held.

All 132 banks in both sectors of the capital united in a daylong strike today to protest the kidnapings two years ago of three Christians who were senior department heads of the nation's central bank.

Thousands of Lebanese have been abducted in the 12-year-old civil war between Moslems and Christians.