Syria is considering a U.N. request to interview six top officials about the slaying of a former Lebanese leader, a Foreign Ministry official said Monday. A Lebanese official said earlier that President Bashar Assad's (search) brother-in-law was among the six.

Assad's regime has been under heavy pressure since the U.N. Security Council unanimously demanded last month that Syria cooperate fully with the inquiry into the assassination of former Prime Minister Rafik Hariri (search), warning of further measures if it fails to do so.

The Foreign Ministry official, who requested anonymity because he was not authorized to speak to journalists, confirmed the request to talk with six officials was received Sunday and said the government was "considering" it.

He declined to disclose the identities of the six or say whether the United Nations wanted to talk with them in Syria (search) or elsewhere.

A Lebanese official close to the investigation told The Associated Press on Saturday that investigators wanted to question six people, including Gen. Assef Shawkat, who is Assad's brother-in-law and chief of Syria's military intelligence service.

The pan-Arab newspaper Al Hayat said the others were Maj. Gen. Bahjat Suleiman, former chief of Syria's internal intelligence; Brig. Gen. Rustum Ghazale, Syrian intelligence chief in Lebanon when Hariri was killed; Gen. Jameh Jameh, Ghazale's assistant in Beirut; Gen. Abdul Karim Abbas, head of Syrian intelligence's Palestinian section; and Gen. Zafer Youssef, head of intelligence's communications and Internet section.

The list did not include Assad's younger brother, Maher Assad, who was named along with Shawkat in an interim report to the Security Council last month by chief U.N. investigator Detlev Mehlis.

The report said Hariri, slain Feb. 14 by a truck bomb that killed 20 other people, could not have been assassinated without the complicity of Syrian and Lebanese intelligence.

Syria, which denies any role in the killing, has rejected the findings as lacking evidence and accused the Mehlis commission of politicizing the issue.

Mehlis' report accused Assad's regime of cooperating only to a "limited degree" and said government officials attended the hearings at which investigators questioned Syrians about the assassination.

In its resolution, the Security Council upgraded the powers of the commission, giving Mehlis the right to question anyone at any location and under conditions of his choice.

Officials from the United States and Britain, which co-sponsored the resolution with France, reiterated Monday that Syria had to cooperate with the inquiry.

British Prime Minister Tony Blair told reporters in London that Syria must respect the resolution as Mehlis had delivered "a very, very serious report for Syria."

In Beirut, the deputy assistant U.S. secretary of state for Near Eastern affairs, Elizabeth Dibble, said: "The ball now is in the Syrian court to cooperate, and (we) very much hope that the Syrian government will cooperate with Judge Mehlis in his investigation."

British Foreign Secretary Jack Straw indicated the European Union would not invite Assad to a Euro-Mediterranean summit this month, apparently in displeasure over Syria's lack of cooperation. Straw said only the Syrian foreign minister was being asked to come.

Washington also has accused Syria of letting foreign extremists cross its border to join the insurgency in Iraq and of supporting Palestinian militant groups. Syria denies that.

Syrian Foreign Minister Farouk al-Sharaa reiterated Monday that Syria is "keen" to cooperate fully with the U.N. investigation, the official Syria Arab News Agency said.

Al-Sharaa was quoted as saying Assad's government wants the commission's work to be "professional, aimed at uncovering the truth" about Hariri's assassination.

Syrian Prosecutor-General Ghada Murad said a special judicial committee named to look into Hariri's killing began reviewing information on Thursday from individuals, faxes and e-mails and had questioned several witnesses. She declined to elaborate.

Murad told reporters the committee will cooperate with the U.N. team and Lebanese authorities, "within legal frameworks and on the principle of the accused are innocent until proven otherwise."

The killing of Hariri, who was seen as an opponent of Syrian influence in Lebanon, was a turning point in relations between the two neighbors.

Lebanese staged mass demonstrations against Syria and international pressure on Assad's regime increased, forcing the withdrawal of Syrian troops after a 29-year military presence.