The security chiefs want to temporarily step down during the mission of a UN investigation into the killing of former prime minister Rafiq al-Hariri, the state news agency said on Friday.
General Security chief General Jamil Sayyid and General Ali Haj, head of Internal Security Forces, presented their offer in writing to Prime Minister Najib Miqati, the agency said.
Sayyid and Haj were among several security leaders whose removal has been demanded by the opposition for suspected direct or indirect involvement in the killing.
"I put myself at the disposition [of the prime minister] from the moment the international inquiry commission starts its work and until it completes its mission," Sayyid said.
"In accordance with the recommendation of the United Nations, I will not exercise my functions during the period that the commission is working," he said.
Speaking to Aljazeera, Lebanese opposition minister of parliament Jean Oghastian described the offer made by the two security chiefs as illegal, saying a government official has no right to put himself at the disposal of the government.
"The two security officials have no right to determine the duration of their stepping aside, because these decisions could be made by the interior minister only," Oghastian said.
"The two security chiefs could only resign or take a leave without pay," he said.
Miqati said after a cabinet meeting on Friday the government was committed to meeting demands for the firing of security chiefs. He said he welcomed Sayyid's initiative.
The prime minister also said parliamentary elections would be held by 29 May, two days before the expiry of the legislature's mandate.
Sayyid has put himself at the
disposal of the prime minister
Miqati said he was sending to parliament a proposed mechanism to hold elections within the constitutional deadline.
But he warned that if parliament did not approve the proposed mechanism, his cabinet would call an election. "If the honourable parliament does not approve, we will be forced to call the electoral bodies a month before May 29, that is April 29, in order to conduct elections on May 29," Miqati said.
It was the first time a government leader in Lebanon gave a fixed date for the elections. The proposal, which Miqati did not disclose, appears to serve as a compromise between demands of the pro- and anti-Syrian camps.
Oghastian told Aljazeera: "The announcement meets the demands of the opposition as well as the demands of all Lebanese people."