Security agencies Saturday sealed off several city roads , conducting security checks ahead of the high-level affair.
Among the countries who have confirmed are Burundi, Comoros, Congo Brazzaville, Ghana, Libya, Mozambique, Namibia, Rwanda, Sahrawi Republic, Senegal Seychelles and Sierra Leone.
Others are Somalia, Tanzania, Uganda, Zimbabwe, Gambia, Mauritania, Nigeria, Zambia,Djibouti and United Nations Secretary-General,(UNSG) Antonio Gutteres.
Pakistan's caretaker Prime Minister Anwaarul Haq Kakar had confirmed but cancelled plans to attend due to protests over the cost of power bills.
Ruto has championed the event, themed "Driving Green Growth and Climate Finance Solutions for Africa and the World", which organisers say "aims to address the increasing exposure to climate change and its associated costs, both globally and in Africa".
"The Summit will serve as a platform to inform, frame, and influence commitments, pledges, and outcomes, ultimately leading to the development of the Nairobi declaration," reads the summary of the event, published on its official website.
The meeting is a big deal for the president, owing to his vocal advocacy for more inclusive climate action. Ruto is the current chairperson of the Committee of African Heads of State and Government on Climate Change, a role he inherited from former President Uhuru Kenyatta.
In the one year he has headed the climate change committee, the president has made climate action a key pillar of his national and regional agenda, proposing a united push by African nations to combat the effects of climate change.
Ruto has received praise among his peers for his climate change efforts. France's President Emmanuel Macron recently praised Ruto's initiatives.
"President Ruto is committed to that effort (climate action) and I commend him for that. France and its friends will stand alongside him," Macron said last week.
Ironically, his government's recent lifting of the logging ban cast doubt on his commitment to fighting climate change and Ruto faced widespread criticism. He defended the move as one that would boost the economy. The climate summit offers the chance to set the record straight on the logging subject.
Ruto has urged African unity on many other issues, earning standing ovations for his fiery pan-Africanist speeches on countless foreign platforms. He has slammed coups whenever they have occurred, urging respect for democracy. The Head of State has also been vocal in pushing for a speedy resolution of the ongoing war in Sudan.
Africa's unity, Ruto has insisted, would earn it a seat at the global decision-making table, as well as open doors of business opportunity in the green energy sector. Africa's youthful population, he has added, offers the world valuable human capital.
Ruto's call for debt restructuring and an all-inclusive global financial management has also set him as a champion for the continent's interests. Ruto made such calls during his inaugural address to the UN General Assembly last year, where he urged the World Bank, the International Monetary Fund, and other lenders to consider extending relief to debt-stricken African nations.
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The president continues to unsettle some with his de-dollarisation push and his bold criticism of the West for sidelining African nations.
Although his presidency has been punctuated with diplomatic blunders, Ruto has proven a charmer, hosting several heads of State and government. His latest State guest was Indonesia's President Joko Widodo, with whom they agreed on several trade deals a fortnight ago.