Despite Beijing's repeated protests and warnings of serious consequences for Sino-US relations, Washington, as always, went its own way over the weekend and gave the nod to a massive arms sale package to Taiwan.

This is the stance the US has taken vis-a-vis a "stakeholder" - and sometimes "constructive partner" - terms that it uses to describe China's ties with the world and itself.

Uncle Sam's $6.4 billion arms package to equip Taiwan, including Patriot anti-missile systems, Black Hawk helicopters and Harpoon missiles, reminds us how grudgingly Washington sees China's rise and its unwillingness to see compatriots across the Straits live in peace.

Washington's arrogance also reflects the stark reality of how a nation's interests could be trampled upon by another.

The Taiwan question is closely related to China's sovereignty and territorial integrity, its core national interests and the national sentiment of 1.3 billion Chinese people.

But more than 20 years after the end of the Cold War, the US is still bent on integrating Taiwan into its defense strategy in Asia, and still dreaming of using the island as an "unsinkable aircraft carrier" to contain China's growth.

We have to forget the pledge that "the United States does not seek to contain China" made by Barack Obama when he was warmly welcomed in Beijing just two months ago. Sincerity is subject to proof of action, not mere words.

The US promised in a joint communiqu signed on Aug 17, 1982 - which forms the cornerstone of Sino-US relations - that "it does not seek to carry out a long-term policy of arms sales to Taiwan". It also pledged that Washington "intends to reduce gradually its sales of arms to Taiwan, leading over a period of time to a final resolution". But how many times has Washington trashed its words for the sake of expediency or other ulterior motives? For the world's only superpower, it now seems that a promise is not a promise.

The arms sale is gross interference in China's internal affairs. It seriously undermines China's national security and national reunification, and thus inevitably casts a long shadow on Sino-US relations.

China's response, no matter how vehement, is justified. No country worthy of respect can sit idle while its national security is endangered and core interests damaged.

The US decision not only runs counter to the common dream of pursuing development and cooperation among the people on both sides of the Taiwan Straits, but also exposes the US' usage of double standards and hypocrisy on major issues related to China's core interests.

Compared with the US, China is still weak, both economically and militarily. The countermeasures that China has taken - ranging from repeated protests to plans to halt military exchanges and punish US companies involved in the arms sale - may not be forceful enough to compel Washington to mend its ways. But a message has to be sent loud and clear: If the US shows no respect to China's core interests, it cannot expect cooperation from China on a wide range of major regional and international issues.

China must make sure that it means what it says.