Moody's Investors Service warned Wednesday it may downgrade its credit rating for Toyota Motor Corp. due to the financial fallout from suspended car production following the March 11 quake and tsunami.

The warning came as Toyota, the world's No. 1 carmaker, is struggling to resume output in Japan after the twin disasters disrupted supply chains and caused shortages of parts.

Toyota is currently running just two plants at limited capacity after halting production at all 18 factories in Japan from March 14 to 26.

Toyota said Wednesday it would resume limited production at its plant in Kanagawa, west of Tokyo, on Monday. The Kanagawa factory will make the Corolla Axio and minivan Raum models.

But Toyota spokeswoman Shiori Hashimoto said it remained unclear when Toyota would return to full production in Japan. She said the March disasters resulted in a production loss of 260,000 cars from March 14 to April 8.

Moody's said Toyota's financial and operating performance will worsen as a result of the disasters, which are causing major disruptions in auto parts supplies and have forced Toyota and other automakers to halt production.

Amid mounting concern over Toyota's output, the company's share price has dropped nearly 10 percent since March 11 to close at 3,265 yen ($38) on Wednesday.

Mamoru Kato, an analyst at Tokai-Tokyo Securities, said Toyota's production at the two plants accounts for only 3 to 4 percent of normal capacity. The two factories have been making Prius and Lexus cars since March 28.

"There is no question that a plunge in domestic production will really hurt Toyota's earnings," said Kato. "We don't know how long the shortage crisis will last."

Moody's said it would take "many months" for Toyota to return to normal production. Toyota's Hashimoto declined to comment on Moody's warning.

Toyota's long-term uncollateralized debt rating is currently set at Aa2 by Moody's. The rating agency said its review for possible downgrade will focus on Toyota's ability to restore production in Japan.

"Moody's will also consider how quickly the company can improve its profitability despite the negative impact of the disasters," it said.

Japan's top business daily Nikkei said Wednesday that Toyota would resume auto production at most of its domestic plants as early as next week. The Asahi daily said Toyota would reopen the remaining plants under limited capacity. Hashimoto denied the reports.

Car sales in Japan dived nearly 40 percent in March following the tsunami.

Toyota said Monday it is inevitable that it will be forced to suspend production at all of its North American factories due to parts shortages following the March 11 quake.