The government of Premier Selim Hoss today imposed full press censorship in Lebanon, formally muzzling the Arab world's last free press.

The move, clearly in response to strong pressure from Syria, whose troops occupy Lebanona as the bulk of an Arab peace keeping force, was announced after a meeting of Hoss' new Cabinet and President Elias Sarkis.

Although full details of the decree were not available, it appeared from government radio accounts thatforeign correspondents in Lebanon would also come under censorship, as they have occasionally in the past.

Imposition of censorship - which Beirut's most respected newspaper, An Nahar, said it was prepared to accept because of the wartime conditions - was seen by observers as a compromise response to Syrian demands that Lebanon's press be reduced to a small number of rigidly controlled newspapers, patterned after the press in Damascus and most other Arab capitals.

Syrian forces had already shut down eight leftist and independent newspapers in Beirut, leaving open only the handful that fully supported Syria or the rightist Christians, Syria's allies during Lebanon's recently ended civil war.

Hoss said today that he hoped that the censorship, which is to take effect Monday, will allow newspapers closed by the Syrian forces "to resume publication in a short time." It is viewed here as the mildest of the alternatives open to the Lebanese government.

The Cabinet announcement said the censorship will be applied by a committee of security police using ground rules laid down by the government. Cabinet sources said the ground rules would be changed according to the situation in Lebanon and the Arab world.

Observers expect that, in addition to military and security details normally censored in wartime, criticism of Syria and close scrutiny of its activities in Lebanon will be banned from publication.

Many of the newspapers closed by Syrian forces had criticized Syria's entry into Lebanon's civil war as foes of the Lebanese leftists and the Palestinians.

Last week, Lebanese Foreign Minister Fuad Bustros met with Syrian President Hafez Assad in Damascus to discuss the worsening press situation. While Bustros was in Damascus, a spokesman of Syria's ruling Baath Party separately proposed that Lebanon be allowed to have only three papers, reflecting political groupings of the right, left and center, under firm governmentcontrol.

The Baathist spokesman's proposal was seen by some here as a first step by Syria toward installing its own system in Lebanon, with political parties patterned after Syria's and a sharp curb on Western influence in what has long been the most Western of the Arab countries.

Ghassan Tueni, the publisher of An Nahar, who went to Paris after his paper was occupied by Syrian troops last week, told Washington Post correspondent Jim Hoagland yesterday, before the censorship decree, that "we will accept censorship if it is decided by the Lebanese government. This is a war, after all."

Tueni said, however, that he felt strongly that "a free press is the only proper framework for a national debate and a dialogue between various Lebanese factions on what new Lebanese consensus or social contract should emerge new."

Some of the newspapers closed by Syrian forces had vigorously supported the policies of Iraq, Syria's arch-rival. Tueni said that while it might be necessary to end attachments between individual Lebanese newspapers and some Arab governments, "A free press is essential to our achieving the social objectives of democracy and maintaining the free-enterprise system in Lebanon."

Observers here said Damascus was especially sensitive about An Nahar's criticism because, with the paper's reputation, it could have had a significant impact on the Syrian troops in Lebanon.

Press sources here also speculated that Syria, Egypt and Saudi Arabia want control over the last free press in the Arab world to prevent efforts to undermine moderate Arab states' peace negotiations with Israel.

Israel has censorship regulationss covering domestic and foreign news media but applicable only to military matters. There is no political censorship in Israel and little effort to prevent publication of routine military news.

Under today's decree, the Lebanese censorship committee has the power to fine or jail offenders and to close publications violating censorship.

Hoss also said he was reviving dormant laws giving the government the power of prior censorship over magazines, books, films and plays.

In addition to adopting censorship, the newly formed eitht-man Cabinet, which was given broad wartime powers by the Lebanese Parliament 10 days, ago, reduced the number of national holidays from 25 to 14 and placed all rebuilding projects in the ravaged downtown commercial sector of Beirut under government control.

But the Cabinet did not declare martial law in selected areas of Lebanon, as had been expected.

While the Cabinet met, 5,000 cheering, gun-waving Palestinians converged on an uptown stadium to hear their leader, Yasser Arafat, address them on the 12th anniversary of the first guerrilla raid into Israel.

The crowd shout "Long Live Palestine" as Arafat, reviewed a parade of guerilla troops.