Mahathir, 92, a tough-talking political veteran, said he will also bring up the high interest rates levied on Chinese loans used to finance the projects.
Malaysia's previous government under Najib had cultivated warm ties with China and signed a string of deals for Beijing-funded projects.
But critics say many agreements lacked transparency, fuelling suspicion they were struck in exchange for help in paying off debts from a financial scandal that engulfed the state fund 1MDB which ultimately helped bring down Najib's regime.
Mahathir has ordered a review of mega-projects signed by Najib during his nine-year term in a bid to cut the country's national debt, estimated at $250 billion, and other liabilities.
Malaysia on Thursday announced the suspension of three of its largest China-backed projects -- one involving a rail link and two gas pipelines -- worth more than $22 billion.
"I want to go to China as early as possible, but the president of China is not available in July so I will go in August," Mahathir said at a news conference in the administrative capital Putrajaya outside Kuala Lumpur.
"There are several issues to be brought up, among which is the unfairness of the terms of the contracts and also of the loans," he added.
The interest rate charged on the loans to Malaysia "is much higher than when governments borrow," according to Mahathir.
"Normally governments borrow at 3.0 percent and below, but this one is very high," he said.
Finance Minister Lim Guan Eng and Daim Zainuddin, who chairs a top-level economic advisory council drawn from the private sector, are also visiting China separately.
Daim had in May said that all mega-projects in the country would be reviewed by the council and recommendations presented to the government.
The East Coast Rail Link, one of the projects suspended, would connect Malaysia's east coast to southern Thailand and the Malaysian capital Kuala Lumpur.
The $20 billion project was contracted with China's largest engineering firm, China Communications Construction Company, and mostly financed by a loan from the Export-Import Bank of China.
Malaysia's finance ministry said Thursday that 88 percent of two gas pipeline projects costing 9.4 billion ringgit ($2.32 billion) had been paid to the Chinese contractor despite only 13 percent of the work being completed.
In May Mahathir postponed plans to build a high-speed rail link between Singapore and Malaysia, which had been agreed on several years ago, saying it was too costly.
Chinese, Japanese and European investors were among those who had expressed interest in bidding for the project.
Najib was charged with corruption on Wednesday for allegedly accepting millions of dollars in bribe money, in a stunning fall from grace just months after his shock election defeat.//AFP