Apple has reportedly moved to curb the production of new ‘ultrabook’ portable computers by Taiwanese technology  giant ASUS, by forcing its manufacturing partner Pegatron to choose between production contracts for the two companies.

Chinese publication Commerical Times reports that Apple pursued Pegatron after becoming frustrated by the similarities between its MacBook Air and ASUS’ Zenbook, which utilises Apple’s familiar aluminium unibody construction.

It is believed that from the end of March, Pegatron will cease production of ASUS’ Zenbook, resulting in a move to rival manufacturers Compal or Wistron. ASUS has not commented on the reports, stating only that it remains flexible in the industries in which it works and that it will not be limited by such a move.

Pegatron not only assists Apple with its MacBook construction, it is also a key supplier for Apple’s mobile devices. With reports that the Cupertino-based company will debut the iPad 3 this month, it is also thought to be linked to production of the next-generation Apple tablet.

Given Apple’s buying power, a contract from the world’s biggest technology company is likely to be held in higher regard than one of its rivals. The company is known for its early investment in its supply chain partners before production begins, ensuring that it can maximise production output and keep their rivals from squeezing supply components.

It’s an interesting move, some would say anti-competitive. The PC market is in decline yet Apple’s notebook sales continue to defy the trend — if the reports are true, Pegatron knows which horse is on to a winner.