Couillard told a business crowd Tuesday the government should take advantage of the situation to be ready when the recovery in the market comes.
"We shouldn't stop developing our resources when the cycle is down," Couillard said. "Otherwise, we will be overtaken by our competitors."
The Plan nord development project was announced in 2011 by then premier Jean Charest, who hoped to make it a cornerstone of his political legacy.
The government estimated at the time it would generate returns of $80 billion from public and private investments during a 25-year period as well as creating 20,000 jobs.
Couillard did not indicate if he has the same goals, saying his vision of the plan is spread over the next 20 years and he did not want to risk making long-term predictions.
The government will kick in about $63 million to the Plan nord fund this year, with the total amount in the fund rising to $2 billion by 2035.
Asked later by reporters about the amount being invested while his government was tightening spending, Couillard said it's worth the effort.
"There is always a risk with industrial projects," the premier said. "But one thing is certain — people will always need iron ore. A cycle is a cycle. One day it is lower, another day it is higher."
He did say he believes it is possible to stimulate private-sector interest through investments in infrastructure, such as the development of roads in Quebec's north and the negotiation of hydroelectric power rates.
Couillard pointed to a partnership between the province and mining company Stornoway for the extension of Highway 167 to the site where the company operates a diamond mine. That cost the province about $300 million.
"You have to make recovery efforts but at the same time you have to send a message," Couillard said.
The price of many metals, including iron ore and gold, has hit a low point in the last five years partly because of a drop in demand in some emerging countries.
As well, in recent years China's economic growth has fallen below 10 per cent and several economic indicators point to a slowdown in demand from that country.
Couillard is optimistic that prices will rebound soon.
He took a shot at the previous Parti Quebecois government, saying it had sent an economic message that hindered the development of northern Quebec.
Charest, who was also in attendance at the Objectif nord forum, said his government had provided for price fluctuations in metals prices when the Plan nord was conceived.
"There will always be cycles," he said. Now we're in a cycle where resources are down. We knew that when we designed the Plan nord."