As President Barack Obama embarks on his second term, his foreign-policy strategy remains murky.

Clearly, the president wants, and needs, to focus heavily on domestic problems. In his own words: "As we turn the page on a decade of war, it's time to do some nation-building here at home." Granted.

Yet – as events in Mali and Algeria showed last week – the world will not hibernate while America puts its own house in order. If allies and enemies believe Obama's top priority is to disengage from much of the world, the consequences for U.S. security interests will be dire.

Those disturbing consequences are already painfully evident in Afghanistan and in the Middle East.

In Afghanistan, the administration has understandably scaled down its objectives as Americans tire of the country's longest war. The current goal is to leave a country stable enough to prevent the return of al-Qaida or affiliates who want to attack the West.

U.S. officials have trained more than 350,000 Afghan security forces – about half of them police – who are supposed to keep their country stable after U.S. troops exit by the end of 2014. U.S. officials are negotiating with the Afghan government about whether to leave a small U.S. force after 2014. The U.S. military reportedly wants 10,000 to 20,000; the White House is considering 3,000 to 6,000. The purpose would be to provide support in areas such as logistics, intelligence, counterterrorism and air support.

Anyone who follows Afghanistan knows its security forces aren't capable of keeping the peace alone, especially since the Taliban is still potent. A Pentagon report in December said that only one of 23 Afghan brigades was able to operate independently.

Yet the administration has given conflicting signals about whether it wants to keep any follow-on force to give Afghan troops backup and backbone. A senior White House official recently floated a "zero option" – meaning no U.S. troops after 2014. Other officials have indicated that small numbers of U.S. special forces would be sufficient to keep out any resurgent al-Qaida – although it is hard to see how special forces could operate if Afghanistan implodes.

And collapse, or renewed civil war, is what many observers expect if all U.S. troops – or all but a very few – leave next year. Indeed, in the absence of clarity about U.S. intent, Afghan factions are hedging their bets and rearming.

Even Pakistan – a country that has permitted the Taliban safe haven – has made clear it is frightened of a premature and total U.S. exit. Well it should be. If the Taliban retakes control of much of Afghanistan, it would become a base from which Pakistani extremists would try to take control of their nuclear-armed state.

"When people think the United States is walking away from everything, it really has an impact," says former U.S. Ambassador to Afghanistan Ronald Neumann. Into the vacuum that is created, bad forces flow.

Similarly, the administration's disengagement from the Middle East has also had negative consequences. Even where leading from behind was effective – in Libya – the administration failed to follow up, though it was clear the regime's collapse meant pilfered arms would flow freely across the region.

But the most ugly example is Syria, where the administration has been reluctant to lead at all.

U.S. officials hesitated for months over whether to identify and possibly arm moderate Syrian rebels. In the meantime, money and weapons poured in from the Arab gulf to a minority of Islamists and jihadis who seized leadership of the rebellion.

Finally, in November, U.S. officials helped organize a new, broad-based civilian Syrian Opposition Council. Washington also encouraged the Saudis – yes, the Saudis, who support militant Islamists around the globe – to try to organize Syrian rebel leaders into a coherent fighting force. So far the effort has failed, with moderate commanders shorted of guns and money.

Meantime, the Syrian Opposition Council is floundering, because promised funds have not arrived. (U.S. leadership, anybody?) Message: Without strong and consistent U.S. pressure and backing, no moderate Syrian rebel leadership will emerge.

But ambivalence at the top makes such support unlikely. The region recognizes that the White House really doesn't want to get involved in the Syrian struggle, no matter who fills the vacuum.

U.S. officials, however, are busy planning for what to do after the fall of Bashar Assad. Never mind that their influence will be minimal, because hard-line Islamists will have won.

White House ambivalence on Afghanistan and avoidance on Syria are widely noticed in other regions. The perception is of an administration that wants disengagement above all, but won't admit the likely consequences – even to itself.

No doubt Iran notices. And China. And al-Qaida's franchise operations in many places.

The issue is not whether the United States should heedlessly engage in more wars (it shouldn't) or engage more at home (it should), but whether it is disengaging too fast from regions where its leadership is still needed.

Whether Obama can – or is willing to – juggle engagement both at home and abroad will define the legacy of his second term.

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