Maru held a meeting with Chinese charge de affaires Chen Jiliang during which he reaffirmed PNG's commitment to a proposed free trade agreement with China.
He said the study would determine the cost and benefits of such an agreement.
"Both parties need to agree to the terms of reference for the study, and agree to hire a neutral independent global expert to undertake the study. Without that, we cannot proceed with the study," he said.
He hopes that by January or February next year, the countries should be discussing the implementation of the study's recommendations.
It was one of the outcomes of talks between the former Prime Minister Peter O'Neill and Chinese Premier Li Keqiang in 2016.
It was reaffirmed by Prime Minister James Marape during a visit to Beijing last year.
Maru thanked the Chinese government for providing K1 million for PNG to engage a consultant to undertake the PNG side of the study.
He is also requesting local and international investors to partner with the government in the downstream processing industry.
"We need local and international investors to support the government in aggressively pursuing its new policy direction of replacing all food imports by investing in the downstream processing industries," he said.
He said PNG must process coffee, cocoa, coconut and fish before they are exported.
"They should also invest in large-scale oil palm plantations in the savannah land especially in the Sepik Plains, Western, Madang and Morobe, and in cattle and other agriculture projects as well, and in the PMIZ," he said.