Toyota may boost exports from Japan for the first time in three years to meet its global sales target because it is facing capacity restraints in North America.

Weak sales in resource rich and emerging countries have made it "very difficult" to meet the 2015 target, managing officer Yoichi Miyazaki said last month, Bloomberg News reported, citing a union newsletter.

Toyota must make up for the shortfall by boosting sales in developed markets, Miyazaki said, asking for workers' cooperation in handling the increased workload in Japan.

"Whenever there is a letter from the management to labour, the outlook is always ultra-conservative," Koji Endo, an auto analyst at Advanced Research Japan, told the news agency. "Compared with the very conservative numbers that management has been giving to the union, the actual number is probably going to be better."

Miyazaki didn’t identify specific countries in his letter but Toyota has recently forecast stronger sales in North America will be offfset by weaker demand from Russia and the Middle East due to plunging oil prices. Toyota spokeswoman Kayo Doi confirmed the contents of the newsletter to Bloomberg but declined to comment further.

Toyota exports from Japan fell 3.3% this year to the end of April. The automaker shipped 5.8% fewer vehicles abroad last year and 2.4% in 2013, despite policies introduced by prime minister Shinzo Abe that weakened the yen with the aim of boosting exporters and stimulating the economy, Bloomberg noted.

Toyota is approaching capacity limits in North America and is to build a new factory in Mexico but that plant won’t begin Corolla output until 2019.

Jim Lentz, head of Toyota North America, said in January the company would turn to Japan for more RAV4s and Lexus RX units (both made mostly in Canada) to keep up with booming US demand for SUVs, the report added.