King Abdullah "asserted the need to consolidate and strengthen Syrian-Lebanese relations", said a joint Saudi-Syrian statement issued after the summit in the Red Sea city of Jedda.
Al-Assad is facing mounting international pressure over the killing last year of Rafiq al-Al-Hariri, the former Lebanese prime minister, with a UN probe into the assassination wanting to interview him over his alleged role.
Al-Assad flew to Jedda on Sunday to discuss the growing crisis over al-Hariri's 14 February killing in a Beirut bomb blast in which the UN probe has already implicated Syrian and Lebanese officials.
The death sparked popular protests against Syria's domination of Lebanon, leading to the departure of thousands of Syrian troops from its smaller neighbour in April after a near 30-year presence.
Later on Sunday al-Assad flew to Egypt for talks with Hosni Mubarak, the Egyptian president.
The leaders discussed developments in Syria and Lebanon at the resort town of Sharm al-Shaikh for about an hour, before al-Assad flew back to Syria.
The MENA report said: "The meeting of the two leaders covered the results of talks President Mubarak had with the Saudi king ... and with French President Jacques Chirac in Paris ... and with Lebanese leaders and the UN about Syria and Lebanon,".
The meeting discussed earlier talks
Mubarak (L) held with Saudi Arabia
Imad Shuaibi, a Syrian political analyst, said: "It seems that there are Saudi and Egyptian efforts to find a comprehensive regional and international agreement regarding the UN request to meet President Assad.
"The UN request violated (international) protocol by naming the witnesses whom the commission wanted to meet."
Lebanese-Syrian relations should be improved "in all sectors in order to protect the interests of the two brotherly countries and the security of the region", said the statement read on Saudi state television.
The president said in remarks published on Saturday that he would only agree to testify to the UN team if the request had a legal basis.
Khaddam (R) has testified in the
UN probe into al-Hariri's killing
The pan-Arab daily al-Hayat, quoting diplomatic sources, reported on Sunday that Farouk al-Sharaa, the foreign minister, who accompanied al-Assad to Jedda, had written to the UN inquiry agreeing to be interviewed but stating al-Assad was still "studying" the request.
The letter stresses "the Syrian president's immunity" and that his questioning would "violate Syrian sovereignty", according to al-Hayat.
Abd al-Halim Khaddam, the former Syrian vice-president now in exile in Paris, has accused al-Assad of personally threatening al-Hariri a few months before the former Lebanese leader's murder.
In a series of explosive interviews with Arab and Western media, Khaddam also openly called for the overthrow of the government he served so long.
The 73-year-old former Baath party stalwart called on the opposition to work together, including the Muslim Brotherhood, which has been banned on pain of death in Syria since 1980.
But Khaddam stressed he was not calling for foreign help in ending the iron grip which al-Assad's Baath party has held on Syrian political life since 1963.
By contrast, a leading Lebanese opponent of Damascus, Druze leader Walid Jumblatt, warned that foreign help would be essential.
"The dictatorship cannot be eradicated by words or emotions. It can only be removed with international help and the backing of both the internal and external opposition," he said in Beirut.
Jumblatt (R): Words or emotions
cannot remove the Syrian regime
In Riyadh, a Saudi official on Sunday slammed the war of words between Lebanon and Syria, "particularly the voices in Lebanon which have called for regime change in Syria".
"Regime change in Syria is not required. Even the United States and France do not call for regime change in Syria ... the aim is to find the assassins of Rafiq al-Hariri and bring them to justice," he said.
Saudi Arabia has traditionally had strong ties with Syria, although they were shaken by the killing of al-Hariri, who had dual Saudi-Lebanese nationality.