Swiss drugmaker Novartis's plant in Colorado, has just passed an inspection by U.S. regulators, giving it hope that quality control problems in its North American plants are being solved.

Last December, the U.S. Food and Drug Administration cited Novartis for significant violations of manufacturing regulations at its three generic drug plants in Colorado, North Carolina and Quebec, Canada.

Chief Executive Joseph Jimenez told the Finanz und Wirtschaft newspaper in an interview on Friday that Novartis had been working since January to bring quality standards back up to the level of other Novartis plants.

"In Bloomfield, Colorado, the FDA confirmed to us just today after an inspection that the plant is in such a condition. This development makes me confident. We are on the right track but must not stop," he said.

Novartis's consumer health division has also suffered from manufacturing problems at its Lincoln site, which has annualised sales of $1 billion. Novartis said last month it was taking longer than expected to restart commercial production.

Jimenez has rejected suggestions that a manufacturing glitch that led to Italy banning Novartis flu vaccines last month was the latest in a series of quality control problems.

Italian health authorities lifted the ban on Friday after accepting that the drugmaker had showed they posed no risk to safety. Canadian and Swiss health authorities had already lifted similar bans.