Lebanese President Emile Lahoud says he wants more time as president, months before he ends his six-year term.
The constitution was amended so Lahoud could stand in 1998
A statement issued by his office said he had not completed his political and administrative reform programme yet.
The statement added that if parliament wanted to give him another mandate, he was "ready for the mission".
Lebanon's constitution bans consecutive terms for president, but Syria - which holds overwhelming political power - is thought to want Mr Lahoud to stay on.
Mr Lahoud said late on Tuesday: "If a parliamentary majority wishes to bestow this mission upon me again, then I am ready to accept."
However, correspondents say there is strong across-the-board domestic opposition to changing the constitution to allow him to run.
Washington also urged Lebanon to stand by its current constitution.
"The United States strongly supports a free and fair electoral process in Lebanon," state department spokesman Adam Ereli said. "That means one that is conducted according to the established Lebanese constitution."
Maronite patriarch Nasrallah Sfeir is quoted in the Lebanese press, saying: "The constitution is not just an ordinary law which you can change as you think fit. Each time it has been amended it has led to a serious crisis."
Syria has twice before sought changes to the Lebanese constitution, to extend Elias Hraoui's presidency in 1995 and to allow Mr Lahoud to run while still head of the armed forces in 1998.
Mr Sfeir accused Syria of again interfering in Lebanon, saying politicians who were against amending the constitution "changed their minds after going to Syria".
Several leading Lebanese politicians were last week summoned to Damascus for talks with the Syrian leadership.
Syria has kept thousands of troops deployed in Lebanon since the civil war.
Lebanese presidents and prime ministers are drawn from the Maronite Christian and Sunni Muslim factions respectively - but both need the backing of Syria to take office.