Hosting a Summit of leaders of Germany, Japan and Brazil under the G-4 format here, he said the UNSC "must include the world's largest democracies, major locomotives of the global economy, and voices from all the major continents" to carry "greater credibility and legitimacy".
It will make it more representative and effective in addressing the challenges of the 21st century, he said at the Summit meeting with Germany Chancellor Angela Merkel, Japanese Prime Minister Shinzo Abe and Brazilian President Dilma Rousseff, the first since 2004.
"Our institutions, approaches, and often mindsets, reflect the wisdom of the century we have left behind, not the century we live in. This is especially true of the United Nations Security Council," the Prime Minister said.
"The reform of the Security Council within a fixed time frame has become an urgent and important task," he said, while talking about the modern age challenges like trends in demography, urbanization and migrations.
G-4 is a grouping which has been jointly pushing for reform of the UN Security Council to make it broad-based by including them as permanent members.