Toyota is facing a few challengers in the near-term.

Toyota's United States sales jumped an astonishing 87 percent last month, but the company's chief executive warned on Monday that a slowing economy could hurt sales in the short-term. Toyota's CEO also expressed concerns about Europe's growing debt crisis and the value of the yen.

"In the short run, the European economy and a possible slowdown in the recovery of the U.S. auto market is a concern," Toyota CEO Akio Toyoda told Bloomberg. He added that the yen is also a "major concern."

Despite those concerns, Toyota should finish out the year strong, though, with Toyoda predicting a 21 percent boost to 9.58 million vehicles in Toyota group sales. That growth can be attributed to Toyota's full recovery from last year's earthquake and tsunami.

However, a stronger yen will erode profits and Toyota is already seeing a slow down in the European market. Toyoda brushed off concerns of slowing demand in emerging markets like China, saying there is plenty of growth left.

"Though there is concern over the Chinese economy's outlook, there is still sustainable growth in China, and the buyers are spreading to the middle class," he said.