Canada’s largest home-improvement retailer, Rona Inc., said Tuesday that it has rejected a $1.8 billion takeover offer from Mooresville-based Lowe’s Inc.

But Lowe’s indicated it may press on: The company said it has the support of institutional shareholders who own about 15 percent of Rona’s stock.

“We think this proposal is very important,” said Doug Robinson, Lowe’s head of international development. “We’re not speculating on what the next steps are. We have said to the Rona board we’re still interested in a friendly transaction.”

Lowe’s CEO Robert Niblock echoed Robinson in a statement: “We reiterate our proposal to the Rona board. We hope that in the exercise of its fiduciary duties, Rona’s board will reconsider and recognize that our proposal represents a very attractive opportunity for all Rona shareholders and the company’s major stakeholders.”

The deal, if it were to happen, would be Lowe’s biggest acquisition to date.

Lowe’s offered Rona $14.50 Canadian dollars (which is almost the same in U.S. dollars) per share to acquire the company. That offer, which Lowe’s made July 8, would represent a 37 percent premium on Rona’s pre-offer stock price. Rona’s stock closed at CA$13.50 a share Tuesday, up 13.7 percent.

Rona said it has decided to remain independent after reviewing the offer and to pursue its own strategic plan. But Rona also revealed that Lowe’s would not confirm that it won’t pursue a hostile takeover of the company.

Lowe’s told Rona it “was going to consider all of its options,” the company said.

The unsolicited takeover offer from Lowe’s stirred a defensive reaction from Canadian politicians. “This transaction does not appear to be in the interests of either Quebec or Canada,” Quebec’s finance minister Raymond Bachand said in a statement. He said he and other officials are assessing their options, including the possibility of establishing a fund to “defend Quebec’s interests.”

Based in Boucherville, Quebec, Rona operates about 800 stores, including franchised locations. The company posted a CA$86 million loss in 2011, as revenue was flat, at CA$4.8 billion.

Lowe’s, the second-largest home-improvement retailer in the U.S., has seen its growth slow as the housing market and the economy continue to drag. The company is still significantly larger than Rona, with 1,745 stores and $50 billion in sales last year. Lowe’s has 35 stores in Canada, but none in Quebec.

Over the past year, Lowe’s has taken steps to cut costs, including laying off about 1,700 in-store managers, offering buyouts to hundreds of workers at its Mooresville headquarters and cutting by half the number of new stores it plans to open.

Despite the low-growth environment, Lowe’s has managed to revive its earnings, posting a $527 million profit for its most recent quarter. The company had more than $3 billion worth of cash at the end of May, according to securities filings, and said it could acquire Rona without needing any financing.

Following the news, credit rating agency S&P placed the long-term A- corporate credit rating for Lowe’s on watch with negative implications. The possible downgrade, S&P said, was triggered by Lowe’s apparent increased appetite for risk, combined with increased leverage for debt-financed share repurchases over the past two years.

“Lowe’s has a limited track record of acquiring and integrating companies and it is not clear that the Canadian home improvement market won’t decline further,” S&P wrote. They also pointed out that while Lowe’s operates only big-box stores, Rona has a wide mix, from big-boxes to small plumbing and HVAC outlets.

Robinson, however, said that Lowe’s strategy with international expansion would be to adapt to the local market. Rona’s headquarters would remain in Boucheville, and Lowe’s would keep Rona’s eclectic mix of different store sizes, he said.

Lowe’s stock closed down 5.6 percent Tuesday, at $25.37 a share.