Lebanon's prime minister-designate Saad al-Hariri said on Monday his efforts to form a new government faced "stumbling blocks", casting doubt on hopes for the quick formation of a new administration to steer the country away from political crisis.

Hariri was designated prime minister more than two weeks ago as part of a political deal that saw Michel Aoun, an ally of the powerful Iran-backed Shiite group Hezbollah, fill the presidency that had been vacant for 2 1-/2 years due to political divisions.

Optimistic statements from rival politicians had given rise to hopes the new cabinet would be in office in time for Lebanese independence day, which falls on Tuesday.

But casting doubt on how quickly the government would be formed, Hariri said "there are some stumbling blocks" after meeting Aoun on Monday. "There is someone complicating matters," he said, without saying who.

Tensions have arisen among rival leaders over portfolio distribution, the number of ministries in the new cabinet, and a contentious electoral law which needs to be passed in order for a parliamentary election to happen in 2017.

Lebanon urgently needs effective government to address long-pending economic and development issues such as improving infrastructure, organising refuse disposal, and tapping offshore oil and gas reserves.

Political tensions, exacerbated by war in neighbouring Syria, have paralysed decision-making, and raised fears for Lebanon's stability. The country has had no parliamentary election since 2009.

On Monday, Saudi Arabia, a regional rival of Iran, invited Aoun to visit the country.

Saudi's Prince Khaled al-Faisal, governor of Mecca and an adviser to the king, said during an official visit to Lebanon that Aoun had promised to visit as soon as a new Lebanese government was formed.