Lai Ching-te, the "pro-independence" leader of the ruling Democratic Progressive Party in Taiwan, is set to transit through the United States apparently on his way to attend the inauguration ceremony of newly elected Paraguayan President Santiago Pena. Lai's real goal, however, is not to attend Pena's inauguration but to make a stopover in the US.

For Lai and the DPP, making a stopover in the US is more important than visiting Paraguay. But despite having made "containing China" part of its political and economic strategy, Washington should realize that allowing Lai to transit through the US will further deteriorate Sino-US relations because it would mean the US supports separatist forces on the Chinese island.

Also, Lai is set to transit through the US at a sensitive time — during the campaign for Taiwan election which Lai is contesting as a DPP candidate. By transiting through the US, he can help increase the visibility of the pro-independence forces in Taiwan in the international community and project it as a success to win more votes in the election.

Lai could also interpret his transit as the US' endorsement of his pro-independence policy. But by giving Lai the transit green light, the US has exposed its real position on Taiwan separatist forces. It is natural therefore for the Chinese mainland to doubt that there is a tacit understanding between Lai (and the DPP behind him) and the US administration to target the mainland.

That's why the moment the announcement of his controversial transit was made, the Chinese Ministry of Foreign Affairs condemned the arrangement between Washington and the island's authorities. And Beijing's strong opposition is fully justified under international law.

That there is only one China and Taiwan is an integral part of China is an established fact, a fact recognized by the United Nations and almost all countries, including the US. In fact, in the Joint Communique on the Establishment of Diplomatic Relations between the People's Republic of China and the United States of America, Washington has said: "The United States of America recognizes the Government of the People's Republic of China as the sole legal Government of China. Within this context, the people of the United States will maintain cultural, commercial, and other unofficial relations with the people of Taiwan."

This means the US is obligated under international law to respect the sovereignty of China. In light of the above, allowing Lai to transit through the US is nothing but a violation of both the commitment it has made in the joint communique on the one-China principle and its obligation under international law to respect the sovereignty of China.

Moreover, if Washington is, by default, "endorsing" Lai's candidature in the island's election by allowing him to transit through the US, it would amount to an infringement of China's sovereignty and territorial integrity and interference in the internal affairs of China. That would constitute a blatant violation of both its commitment that the "Government of the United States of America acknowledges the Chinese position that there is but one China and Taiwan is part of China" and its pledge to not interfere in the domestic affairs of China.

China has the right to take countermeasures against such violations of international law. Also, the Chinese government is empowered by Chinese law to take necessary measures, including imposing sanctions, against countries breaching their promises and the separatist forces intent on severing the island from the motherland.

So the US government should stop playing such risky games unless it is determined to spark a fire across the Taiwan Strait which will inevitably spread across the region and will be extremely difficult to douse. For the DPP, Lai transiting through the US in these sensitive times is a further evidence of their design to separate Taiwan from the motherland. What awaits Lai and his fellow separatists in the DPP is punishment according to law.

The author is dean of the School of International Law at the China University of Political Science and Law.

The views don't necessarily reflect those of China Daily.