Saudi Arabia pledged $1.5 billion while the Kuwait-based Arab Fund says Iraq will receive $1.5 billion in infrastructure aid in coming years.
Almost 2,000 delegations confirmed their attendance to the conference for the reconstruction of Iraq, representing governments, private companies and worldwide organizations.
Qatar's Deputy Prime Minister and Foreign Minister said on Wednesday his country was committed to supporting reconstruction in Iraq. The move is seen as a stunning donation as only a generation ago Saddam Hussein invaded the small, oil-rich nation, AP said.
Iraq invaded in 1990, leading to defeat by a USA -led coalition and more than a decade of sanctions.
Wednesday is the last day for the funding to come forward at the summit held in Bayan Palace in Kuwait City.
Daesh came to prominence in Iraq in 2014 when the group captured the northern cities of Fallujah, Mosul and Tikrit, representing nearly a third of the country.
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The United States leads the coalition and hopes that after a three-year fight to defeat the militants it can count largely on Gulf allies to shoulder the burden of rebuilding Iraq.
Of the money needed, Iraqi officials estimate that $17 billion alone needs to go toward rebuilding homes, the biggest single line item offered Monday, on the first day of meetings.
Minister of Foreign Affairs, Shaikh Khalid bin Ahmed bin Mohammed Al Khalifa, affirmed that the Kingdom of Bahrain has continuously supported the Republic of Iraq in its fight against the terrorist organisation of Daesh in building the new Iraq and in the worldwide recognition of the Republic of Iraq.
The conference also represents a move by key Sunni states to support Shia Iraq as part of a wider regional power play to curb Iran's influence in the area.
Prime Minister Haider al-Abadi's government is hoping the global community will follow up the end of major combat against IS, with concrete financial support for reconstruction.