This year's event which is being held under the theme "BRICS in Africa, Collaboration for Inclusive Growth and Shared Prosperity in the 4 Industrial Revolution" is seeking to build on the progress made in advancing the development of the organisation and its member countries.
On Wednesday, he said there would be no victor in a global trade war.
The rapid adoption of mobile telecommunications in Africa and other parts of the developing world, for example, demonstrated how innovation can ignite sudden bursts of development, he said.
Xi held talks with South African President Cyril Ramaphosa in Pretoria on the eve of the gathering, saying that "the Johannesburg summit has special significance for BRICS cooperation in the new circumstances". "A global trade war should be rejected because there will be no victor".
Last week Trump said he was ready to impose tariffs on all $500 billion of imported goods from rival economic superpower China. If you look at Russian economy it's really limping.
Modi said that the 4IR would have more importance than capital.
"This is a trade war, so leaders' discussions are particularly important in coordinating our positions", said Oreshkin.
"Of course, all of us are safeguarding our own sovereignty, we are independent countries, and all of us can choose whoever we want to associate with, and as we associate together in Brics", he said.
The BRICS mechanism has played a positive role in boosting the BRICS countries' economies and global trade, said Ronnie Lins, director of the China-Brazil Center for Research and Business.
Analysts say USA trade policy could give the group some renewed momentum.
The Summit seeks to strengthen the relationship between BRICS member states and Africa.
BRICS Business Council Chair Iqbal Surve said that it is worrying that some countries install trade barriers and this act not only snuffs out healthy enterprises, but also hurts the ordinary people.
"Trade and investment cooperation is the propeller for overarching BRICS cooperation".
"The worldwide community has reached a new crossroads", he suggested. The 2018 Summit will be a seminal milestone for BRICS cooperation, as it represents a decade of BRICS cooperation at the highest diplomatic level.
Those invited included the leaders of African countries, namely, Uganda, Angola, Botswana, Ethiopia, Gabon, Lesotho, Madagascar, Mauritius, Malawi, Mozambique, Namibia, Rwanda, Senegal, the Seychelles, Tanzania, Togo, Zambia and Zimbabwe.
During the Summit, it has become customary for Putin and Xi to meet in-person, at the sideline.