Soviet Foreign Minister Andrei Gromyko has ruled out Soviet military involvement in the Lebanon fighting while pledging full diplomatic and political support for the Arabs, Arab diplomatic sources reported today.

The sources said Gromyko told Farouk Kaddoumi, foreign affairs spokesman for the Palestine Liberation Organization who is visiting here, that Moscow was not prepared to change its Middle East policy and respond to Arab pleas for a show of Soviet strength in the region.

Some PLO leaders had criticized the lack of a more forceful Soviet role, and Kaddoumi is reported to have sought some drastic Soviet action to demonstrate Moscow's backing for the PLO.

Kaddoumi arrived here as part of an Arab League diplomatic drive to lobby with the five states that are permanent members of the U.N. Security Council. The group included Moroccan Foreign Minister Mohammed Boucetta and Kuwaiti Foreign Minister Ahmed Sabah.

Other Arab League delegations plan to have similar talks this week with officials in Washington, Paris, Peking and London.

The Arab sources here said Gromyko firmly rejected any increased Soviet role in Lebanon and apparently ruled out sending Soviet warships or troops to the region. "He made clear this was out of the question," one of the sources said. They did not provide details of Kaddoumi's demands.

Gromyko, however, was reported to have promised to use all Soviet political and diplomatic resources to end the fighting and get Israeli forces to withdraw.

The sources quoted Gromyko as saying the Arabs should take joint actions to secure the Israeli withdrawal and that the Soviet Union stood ready to provide additional weapons.

It was reliably reported that Moscow had replaced all weapons lost by Syria in the Lebanese fighting, a move suggesting a more intensive resupply effort than had originally been reported.

The sources said that the talks between the Arab officials and Gromyko were productive and that there was "no bitterness" over his rejection of Kaddoumi's plea for a tougher Soviet policy line.

The government news agency Tass said the talks were "businesslike and friendly." It quoted Gromyko as underscoring that Moscow was "directing its practical actions and using its weight and influence in international affairs toward preventing mass bloodshed in Beirut and making the aggressor get out of Lebanon."