Speaking in Kuwait at a gathering of the 74-member coalition to defeat ISIS, Tillerson said the war against ISIS is far from over, even in Iraq and Syria.
The plan spans the next 10 years and Iraq announced on the opening day of the conference that the country needs investments worth $88.2bn, of which $22bn were required immediately.
"A lot of the reconstruction we're confident will be undertaken through both public and private sector approaches, and the lending institutions - OPIC, Ex-Im, World Bank, IMF - all of these are important elements of ensuring Iraq has a successful future", he added.
Some 2,300 companies from 70 countries are taking part in the conference, which kicked off on Monday.
Araji said investors in Iraq will find "high risks, but high returns".
U.S. Secretary of State Rex Tillerson says the battle against the terror group ISIL is not over.
"The majority of the damage was to western Mosul as it went through one of the worst and fiercest battles in history", said Nofal al-Akoub, the governor of Iraq's Nineveh province.
"We must continue to enable hospitals to reopen, restore water and electricity services, and get boys and girls back in school".
In an interview with al-Hurra TV, a US-funded Arabic network, Tillerson said the event in Kuwait was not meant to be a donor conference. Meanwhile, Saudi Arabia and other Gulf nations remain suspicious of Iran's influence in Iraq.
US Secretary of Defence Jim Mattis sent a letter to North Atlantic Treaty Organisation last month calling for a formal North Atlantic Treaty Organisation train-and-advise mission, Reuters reported, part of President Donald Trump's campaign for the alliance to do more against militants.
Deputy Prime Minister and Foreign Minister Sheikh Sabah Khaled Al-Hamad Al-Sabah met on Tuesday with EU Foreign Policy Chief and Vice President of the European Commission, Federica Mogherini on the occasion of her visit and participation in the International Coalition Against IS conference and Kuwait International Conference for the Reconstruction of Iraq (KICRI), hosted in Kuwait this week.