US aircraft manufacturer Boeing said on Thursday it had signed contracts worth an estimated USD$600 million with Chinese companies to supply parts until 2021.

The suppliers of the parts, some for Boeing's new 787 airliner, included Chengdu Aircraft Industrial and Hafei Aviation Industry.

"China's aviation industry is providing outstanding technological capabilities and resources that help us meet quality, cost and delivery imperatives in our program -- particularly on the new 787," Boeing executive Carolyn Corvi said in a statement.

Boeing has long bought aircraft parts from China as well as other countries. Components contracts can help a manufacturer sell aircraft in a country.

And Corvi, while emphasizing Boeing's need for quality and value for money, said promoting sales was always a consideration.

Chinese airlines have already ordered 787s.

The Chinese companies would make the parts using their own technology, Corvi said, and Boeing would not have to provide know-how.

Chinese companies, especially manufacturers, have often come under fire for copying foreign products and manufacturing techniques.

"They are very competitive and that's why we're here," Corvi said.