President Cyril Ramaphosa will seek billions of dollars of new spending pledges from foreign investors and local firms at an investment summit on Friday, as he seeks to haul the economy out of recession before next year's election.

The former union leader wants $100-billion of new investments over the next five years and so far has secured pledges for around $35-billion, mainly from China, Saudi Arabia and the United Arab Emirates.

Ramaphosa has made reviving the economy a top priority since taking over from scandal-plagued Jacob Zuma in February, but he has been hampered by severe fiscal constraints and infighting in the ruling African National Congress.

He has said the investment summit will discuss opportunities in sectors including agriculture, manufacturing and energy.

"As an investment destination, South Africa has what it takes to compete," Ramaphosa said in a speech to diplomats on Tuesday. "We are focusing on addressing structural weaknesses in the economy."

The investment summit follows a jobs summit earlier this month at which Ramaphosa announced a wide-ranging set of deals between government, big business and labour which he said would create 275 000 more jobs a year.

Under pressure over his track record on the economy, Ramaphosa has also unveiled a "stimulus and recovery plan" which earmarked funds for job creation and infrastructure development.

The scale of the challenge facing Ramaphosa was underlined by Finance Minister Tito Mboweni's bleak medium-term budget speech on Wednesday, when he unveiled weak growth forecasts and deficit estimates.