Toyota's president believes that the company's rapid global growth is partly behind a rise in quality problems in recent years.

Speaking at a press conference in Japan, company president Katsuaki Watanabe said the company has improved quality controls, and is sticking to its sales targets, including those in North America, despite worries about a credit crunch and a slowdown in the auto market.

AP reported that Watanabe noted the reasons behind the defects were varied, spanning development, design, production, suppliers and maintenance.

But Watanabe said at least some of the problems, including time pressures and shortage of experts, stemmed from the company's dramatic growth in recent years.

"That is not zero," he told reporters, referring to quality problems rooted in Toyota's expansion.

"The fact that Toyota is growing globally suddenly shouldn't be used as an excuse," Watanabe added.

Watanabe said he had ordered a six-month delay in some products since the problems surfaced to tackle quality controls.

Toyota has gone over, one by one, each problem, tracking root causes, analyzing and coming up with ways to prevent a recurrence, Watanabe said.

Watanabe also referred to a trend he dubbed 'big company disease' caused by arrogance among its ranks.

Since 2006, when the worrying rise in recalls began to surface, Watanabe has apologised repeatedly at news conferences in Japan, AP said.