Just three months after Ford started production of the Fusion mid-sized sedan at a second North American plant to keep up with demand, it already has more supplies of the car than it needs.

A Ford spokeswoman confirmed Tuesday in an e-mail that the company has scheduled “approximately” one extra week off in December at its Flat Rock, Mich., plant “as we continue to match production with demand.”

Ford also is shutting its Michigan Assembly Plant near Detroit, where the Focus and C-Max are built, for the same duration.

A report on Tuesday from Morgan Stanley analyst Adam Jonas said Ford executives partially attributed high Fusion inventories to Toyota Motor Sales USA’s “aggressive discounting of the Camry.”

Fusion inventories increased to an 88-day supply as of Nov. 1 from a more ideal 65 days a month earlier, according to the Automotive News Data Center. A year ago, Ford had just 48 days’ worth of Fusions on hand.

Ford had more than a 100-day supply of both the Focus and C-Max on Nov. 1.

Postings by Ford employees on BlueOvalNews.com indicate that the Flat Rock plant could have four more weeks of downtime in the first quarter of 2014 as well.

Fusion sales rose 20 percent this year from January through October, compared with a 2 percent gain for mid-sized cars overall. Early in the year, the Fusion looked to be seriously challenging the segment-leading Camry and Honda Accord, but the Camry has pulled away as Toyota has piled on more incentives.

For the year, Camry has outsold the Fusion by more than 100,000 units.

Toyota’s average incentives increased 8 percent in October from a year earlier, Edmunds.com says. Company executives have said they are willing to offer higher discounts to ensure the Camry retains its title as the country’s top-selling car.

In addition to the Fusion, Ford’s Flat Rock plant also builds the Mustang. The redesigned 2015 Mustang is being unveiled on Dec. 5, with production expected to begin in the middle of 2014.