Randgold Chief Executive Mark Bristow, who will lead the group after the Barrick tie-up, also told Reuters that Barrick could dispose of its Zambian copper mine after the merger.
In Tanzania, the government has accused Acacia, which is 63.9 percent owned by Barrick, of tax evasion and has slapped it with a $190 billion tax charge and banned any exports of unprocessed gold. Acacia denies any wrongdoing.
Barrick shareholders voted on Monday to approve the $6.1 billion all-stock acquisition of Randgold to create the world's largest gold mining company. Randgold shareholders vote on Wednesday.
"The (merger) transaction legally closes at the end of the year," Randgold CEO Bristow said.
But he said that, even before the merger is completed, Randgold "would look to participate as an interested mediator in the interim" in the row between Acacia and Tanzania's government. "The situation is pretty desperate," he added.
Bristow, who will be president and chief executive of the merged firm, did not give specifics about what that mediation would involve but said he would be acting in his capacity as Randgold's chief executive not as the head of Barrick.
Acacia threatened in October to use a bilateral investment treaty to force direct negotiations with Tanzania after Barrick failed to settle the row that has rumbled on for more than a year and a half.
Bristow, who has operated gold mines in Mali and Democratic Republic of Congo, said other priorities were to simplify Barrick’s Africa structure and generate more profits from the company's mining operations in the U.S. state of Nevada.
"This merger is going to require a little bit of chewing gum and walking at the same time," he said.
Bristow said the company would focus on developing copper production where the metal naturally occurs alongside gold, which is the case in its U.S. assets.
He said Zambia's Lumwana mine, where only copper is produced, was a "bit of an outlier". He said the new mining tax laws in Zambia had "really stressed these assets".
He suggested the newly merged company could consider disposing of the Zambia mine, saying it "could do better in other hands, as far as specialist copper operators."
(Reporting by Zandi Shabalala; Editing by Edmund Blair)
By Zandi Shabalala