WASHINGTON - In a bid to step up pressure on Syria, US President Barack Obama on Tuesday criticized Syrian President Bashar al-Assad for missing the opportunity to bring about reform in the country.

"He has missed opportunity after opportunity to present a genuine reform agenda," Obama said on CBS television.

He also slammed the Syrian government for the attacks on US embassy in Damascus, saying "nobody can mess with" the US embassy and the US will take "whatever actions necessary" to protect its embassy.

Obama reiterated that Assad has lost his legitimacy, echoing the remarks by US State Secretary Hillary Clinton on Monday.

"We have been working at an international level to make sure we keep the pressure up to see if we can bring some real change in Syria," Obama said on CBS.

Clinton said on Monday that Assad has lost his legitimacy and Washington has "absolutely nothing invested in him staying in power," in one of the toughest rhetorics by senior US officials on Syria.

She made the remarks after the US embassy and the ambassador's residence in Damascus were attacked by Assad loyalists on Monday. The attacks were apparently triggered by the controversial visits by US Ambassador Robert Ford and French Ambassador Eric Chevallier to the central Syrian city of Hama, which has been gripped by anti-government protests.

Syrian Foreign Ministry vehemently denounced a statement by Clinton, saying it posed an additional evidence about the US "flagrant intervention in Syria's internal affairs."