Undated (AP) _ Newspapers in most Western nations on Wednesday supported the United States' right to send its fleet into the Gulf of Sidra, but news media in Arab and Third World nations denounced America's retaliatory attack on Libyan ships and radar.

Western papers supported the U.S. assertion that the Gulf of Sidra is in international waters and offered advice ranging from calls to oust Libyan Col. Moammar Khadafy to cautioning against future terrorist counter-attacks.

London's conservative Daily Telegraph said: ''There is no international sanction for Khadafy's claim to sovereignty over the Gulf of Sidra and his 'line of death' is a dangerous pretension.

''The United States was right to challenge that pretension. Its fleet was entirely within its rights, too, in retaliating when fired on,'' the Telegraph said.

The Times of London editorialized: ''Restraint towards such an obvious villain as the Libyan leader may be hard to bear. But in the wildly unpredictable circumstances of today, it is much the wisest thing.''

Israel's mass circulation Maariv wrote that ''Washington and Jerusalem have to know that a terrorist reaction will come against innocents. The problem can only be solved with the removal of Khadafy ...''

Some Arab papers, commenting on the 21-member Arab League's unanimous motion of support for Libya, noted Khadafy first broke ranks with fellow Arab countries by supporting Iran in its 5 1/2 -year-long war with Iraq.

Kuwait's radical daily Al-Rai Al-Am denounced America but accused Khadafy of being the ''first to deal the Arab common defense charter a death blow by publicly siding with Iran against Iraq.''

Most pro-Western Arab withheld public comment, provoking the United Arab Emirates' government-owned newspaper Al-Ittihad to express ''surprise at this silence in the Arab capitals regarding the aggression on Libya.''

''Have we forgotten the scars caused by American and Israeli stabs in the Arab body?''

The executive editor of the government-owned Jordanian daily Sawt Ash- Shaab, wrote a vehement page-one column saying Khadafy had attempted to ''split the people, divide the Arab regimes.''

''Not a single drop is left of your patriotism after you slaughtered us with your hands ... If you want us again, you have to come back to the fold,'' Tareq Masarweh added.

The Japanese newspaper Tokyo Shimbun said: ''The United States should be irritated by the speech and behavior of Libya, which sneers at it, but the U.S. 'gunboat policy' to slap a hateful small nation is childish.''

The Hungarian Communist Party newspaper Nepszabadsag compared the ''Tonkin Bay incident that was a pretext for triggering the Vietnam War'' with ''the planned military provocation, entirely unjustifiable'' by the U.S. Navy in the Gulf of Sidra.

The editorial in the Kenya Times, published by the Kenya African National Union of President Daniel arap Moi, typified Third World attitudes:

''Khadafy might have his shortcomings, too, but to associate every terrorist action or activity with him is a little bit far fetched.

''Reagan is guilty of the same crime for supporting the racist South African regime and UNITA (anti-Marxist rebels) in Angola, without mentioning the recently abortive attempt at giving the anti-Sandinista Contras of Nicaragua $100 million for their insurgency against the Nicaraguan government.''