IT was revealed in Washington last week that the United States top diplomat, Secretary of State Hillary Clinton, will leave her post at the end of next year.

She will do this even if President Barack Obama wins a second term in office and asks her to stay on.

It is unclear whether she is doing this in order to prepare for another presidential bid herself, or whether she has policy differences with Obama, or whether she simply wants a break.

Either way, the surprising news is already causing palpitations in capitals across Southeast Asia.

To understand the reason why, it is only necessary to recall the performance of her weak and unlamented predecessor, Condoleezza Rice, who was routinely sidelined by the Defence Secretary Donald Rumsfeld.

As Jeffrey Bader, now Asia director at the National Security Council, once told me over lunch in Washington: “Rice is afraid of Rumsfeld. He shows her no respect and often refuses to take her calls.”

A supposed Russian specialist, Rice focussed her attention largely on the Middle-East, Europe and China. Southeast Asia was very much an afterthought for her.

Indeed, she even broke a longstanding American tradition and declined to attend the annual ministerial meetings of the Association of Southeast Asian Nations.

Her absence was viewed as confirming the relative lack of interest that the United States showed towards this region at that time.

Thankfully, all that changed when the strong-willed Clinton became secretary of state in 2009.

Together with her pragmatic Assistant Secretary Kurt Campbell, whom I also knew in Washington, she promptly and unequivocally restored warm and close ties with the region.

This re-engagement occurred even in such repressive places as Laos, Myanmar and Vietnam, because Clinton embraced Obama’s decision to talk to, rather than to shun, these unliked regimes.

Her proactive stance helped calm ASEAN anxieties over the way Beijing sought to assert sovereignty and “core interests” in the South China Sea.

Indeed, it was because Clinton and Campbell, backed by Bader, effectively told China to ease off that Washington’s ties with the region got back onto a solid footing.

At last July’s ASEAN Regional Forum in Hanoi, Clinton declared that “freedom of navigation, open access to Asia’s maritime commons and respect for international law in the South China Sea” are in America’s “national interest.”

In other words, China could not rule the waves over the whole sea itself.

Beijing was enraged, but this region’s leaders were almost visibly whooping and cheering.

Clinton’s declaration, along with other moves, constitute what she has called America’s “forward deployed diplomacy” in Southeast Asia.

It includes Washington signing the Treaty of Amity and Cooperation, as well as Obama hosting a US-ASEAN Summit and confirming he will attend this year’s East Asia Summit in Jakarta.

Clinton has also said that the US views ASEAN as “the fulcrum” of Southeast Asia’s emerging regional architecture.

Despite these reassuring moves, the impending departure of their prime mover, Clinton, has caused worries to resurface about whether the US will sustain its engagement.

If she were to be replaced by someone like Rice, those concerns would certainly be justified.

And that is why governments here would appreciate a concrete, pre-Clinton departure signal of longterm fealty to the region.

Said Ernest Bower, Southeast Asia director at Washington’s Centre for Strategic and International Studies: “Clinton should seal her legacy as ‘the Pacific secretary’ by working to put enduring institutions in place to underpin the US commitment to the region.”

He is right. After all, ASEAN is America’s fourth-largest export market and its fifth-largest trade partner, with around US$150 billion in total two-way trade last year.

A good time for Clinton and Obama to do this would be at October’s East Asia Summit and at November’s APEC Summit in Honolulu.

If that happens, there would be no need to fret about Clinton’s impending exit.