"The amount is 500 million dollars," Swedish Aid Minister Carin Jämtin told a press conference.
Representatives from 60 donor countries and organizations are to meet in the Swedish capital on Thursday to raise money for Lebanon's immediate needs.
"This money is needed to get the country started," Kathleen Cravero, the head of the United Nations Development Program's (UNDP) bureau for crisis prevention and recovery, added.
Lebanon's ambassador to Sweden, Mounir Talhouk, said thousands of people had been left homeless following Israel's bombings of southern Lebanon.
"Lebanon was not prepared for such a catastrophe," he said.
"We have the displacement of people. We have problems with water distribution, electricity. We do not have pre-prepared shelters" to house the homeless, he said.
Jämtin, whose country has already contributed 10 million dollars in humanitarian aid to Lebanon, said Sweden would contribute another 20 million dollars, or four percent of the amount needed.
Among those expected to attend the conference, organised together with the Lebanese government and the United Nations, are Lebanese Prime Minister Fuad Siniora, as well as foreign or aid ministers from numerous EU countries, several EU commissioners, and representatives of South Korea, Japan, Brazil and Morocco.
Senior officials from the United States and the United Nations, the World Bank, International Monetary Fund, Red Cross and World Health Organization are also expected.
Israel's military offensive in Lebanon, which began on July 12 and ended on August 14 and pitted the Israeli army against the Lebanese Shiite militia Hezbollah, has caused damage estimated at 3.6 billion dollars by Lebanese authorities.
Another conference on the long-term reconstruction of Lebanon is to be held in Beirut at the end of the year.