宣称 (xuānchēng) means 'to assert, to claim' and is used for formal, public statements of fact, often by authorities, companies, or scientists. It is more formal and deliberate than 声称 (shēngchēng), which is also formal but can be more neutral or reportive; 自称 (zìchēng) specifically means 'to claim to be' (a role or identity).