Dublin-based pharmaceutical group Shire on Tuesday said it had bid $30 billion (27 billion euros) for US rival Baxalta to form a global biotech company focused on rare diseases.

"We believe the proposed combination of Shire and Baxalta would be strategically and financially attractive for both of our companies, accelerating our respective growth ambitions and creating the leading global biotech company in rare diseases," Shire's Chief Executive Officer Flemming Ornskov said in a statement.

Shire said a tie-up would generate $20 billion in product sales by 2020.

The hostile all-shares bid made on July 10 was pitched at $45.23 per Baxalta share.

Flemming said it was Shire's "strong preference to immediately enter into a negotiated transaction to explore the full potential of the proposed combination and finalize the terms of an agreement".