Insurance companies that provide protection to Sears Holdings Corp. suppliers have scaled back policies in recent months, people with knowledge of the matter said, following seven years of declining sales at the department-store chain.

Insurers such as Coface SA and American International Group Inc. have reduced the size of so-called trade credit policies for existing Sears vendors or declined to provide protection for new suppliers, according to the people, who asked not to be identified because the matter isn’t public. AIG has cut the size of some new policies by as much as 50 percent, one person said.

Insurance companies sell policies to reimburse manufacturers if a retailer is unable to pay for their goods. With less coverage, vendors may decide to sell smaller quantities or even stop supplying products to Sears. They could also purchase credit derivatives, a more expensive way of insuring they are protected in the event of nonpayment.

Suppliers find it harder to get coverage for the retailer than any other chain, one person said. Still, Sears’s vendors have faced similar tightening in the past and it eventually subsided, according to the person. Sears suppliers also aren’t alone in seeing cutbacks. Insurers are being more cautious on some other retailers that sell electronics, which have slim profit margins, and appliances, which are expensive to produce.

Howard Riefs, a spokesman for Hoffman Estates, Illinois- based Sears, said today that the company’s ties with vendors are strong and it hasn’t seen any disruption in the flow of products.

“We have ample liquidity to run the business,” he said in an e-mail. “Sears Holdings is a company rich with flexible assets, which can be reconfigured to fund our investments in our transformation.”

Jon Diat, a spokesman for New York-based AIG, declined to comment. Maria Krellenstein, a spokeswoman for France’s Coface, didn’t return phone messages.

The clampdown may add to the challenges facing Sears Chief Executive Officer Edward Lampert, who is trying to rebound from 28 straight quarters of sales declines and a $1.37 billion loss last year. He’s using a range of tactics to boost revenue, including investing in Sears’s e-commerce operation and its Shop Your Way loyalty program.

The company said earlier today that it was considering a sale of Sears Canada and was hiring bankers to evaluate its options. Sears owns 51 percent of the $1.5 billion business, following a partial spinoff in 2012.

Sears burned through $1.1 billion in cash last year and has sold or spun off assets to replenish its coffers, including $1 billion in real estate sales and the spinoff of its Lands’ End clothing business last month.

Sears’s stock fell 3.2 percent to $41.83 as of 3:12 p.m. in New York. Through yesterday, the shares had fallen 4.5 percent over the past 12 months.

The cost for Sears creditors to protect against a default by the retailer has surged in the past year in the derivatives market. Credit-default swaps maturing in five years have climbed to 25.5 percentage points upfront, meaning it would cost $2.55 million initially, in addition to $500,000 annually, to insure against losses on $10 million of obligations, according to data provider CMA. That’s up from 4.5 percentage points upfront a year ago, according to CMA, a unit of McGraw Hill Financial Inc. that compiles prices quoted by dealers in the privately negotiated market.