PARIS - No sooner did US President Barack Obama welcome home American troops from Iraq and laud that country's stability and democracy than an unprecedented wave of violence - across Baghdad and elsewhere - revealed the severity of Iraq's political crisis. Is that crisis an unfortunate exception, or, rather, a symptom of the failure of Obama's Middle East diplomacy, from Egypt to Afghanistan?

Upon taking office, Obama set four objectives in the Middle East: stabilise Iraq before leaving it; withdraw from Afghanistan from a position of strength and on the basis of minimal political convergence with Pakistan; achieve a major breakthrough in the Middle East peace process by pushing Israeli Prime Minister Binyamin Netanyahu to freeze settlements; and open a dialogue with Iran on the future of its nuclear program. On these four major issues, Obama has clearly achieved little.

With regard to Iraq, since George W. Bush's presidency, the United States has strived to exert a moderating influence on Shia power, so that the country can create a more inclusive political system - specifically, by passing a new law on sharing oil-export revenues among the Shia, Sunni, and Kurdish communities. Unfortunately, the precise opposite happened.

Kurdistan has embarked on a path toward increased autonomy, while the Sunnis are increasingly marginalised by a sectarian and authoritarian Shia-dominated central government. This has implications for the regional balance of power, because Iraq is growing closer to Iran in order to offset Turkey, which is seen as protecting the Sunnis.

Iraqi Prime Minister Nouri al-Maliki's remark during a recent trip to Washington that he was more concerned about Turkey than Iran exposed the huge gulf between Iraq and the US, which now appears to have lost all significant political influence on Iraqi affairs. Indeed, in a disturbing development, the US decided not to play its last remaining card in dealing with al-Maliki: arms sales.

There can no longer be any doubt that the occupation of Iraq was a huge strategic defeat for the US, because it ultimately served only to strengthen Iran. Yet Obama lacks a medium-term vision to deal with the seriousness of the situation - an oversight that, sooner or later, will cost the US dearly.

One of two things will happen: either tighter containment of Iran through sanctions on oil exports will produce positive results and weaken Iran, or containment will fail, leading the US inexorably toward a new war in the Middle East. It is not unlikely that some in US foreign-policy circles regard the deepening Iraqi crisis as a building block in constructing the case for military intervention in Iran.

But Obama is nobody's fool. He has registered the US Congress's hostility toward Iran and the desire to confront the Islamic Republic militarily. He believes, however, that he can avoid extreme solutions; in diplomacy, anything can happen, and the worst-case scenario is never guaranteed.

The problem is that Obama has a strong tendency to overestimate America's ability to influence weaker actors. What is true for Iraq is also true for Afghanistan: Obama can pride himself on having eliminated Osama bin Laden, which was undoubtedly a success, but one that failed to address the root of the problem. Despite a 10-year military presence, involving the deployment of more than 100,000 troops at a cost of US$550 billion, the US still has not succeeded in creating a credible alternative to the Taliban. Worse, its political alliance with Pakistan has frayed.

Indeed, US-Pakistan relations have regressed to their level before September 11, 2001, a time marked by deep mutual distrust. Pakistani leaders obviously bear a heavy responsibility for this state of affairs. But if the US has been unable to involve Pakistan in resolving the Afghanistan conflict, that failure simply reflects America's refusal to give the Pakistanis what they wanted: a shift in the regional balance of power at the expense of India.

Pakistan, accordingly, froze cooperation with the US, because its leaders no longer saw much to gain in fighting the Taliban. The risk is that when the American withdrawal from Afghanistan begins - a process that has just been brought forward to next year, from 2014 - the US will again seek to impose sanctions on Pakistan, an unreliable nuclear state that will react by strengthening ties with China and deploying Islamist terrorism.

Obama also sought to use America's influence to resolve the Israeli-Palestinian conflict as part of his strategy for the broader Middle East. He initially thought that by pressuring Netanyahu to freeze settlements, he would succeed in reviving the peace process. But he was quickly and skillfully outmaneuvered by his ally, who knows how important the Israeli issue is to US domestic politics. By putting Obama at odds with the rest of the US establishment, Netanyahu forced him to retreat.

In 2009, Obama envisioned a settlement of the conflict through the strong commitment of the international community. In 2011, he asserted that only both sides' willingness could ensure a successful outcome. Clearly, the US cannot do much to resolve the conflict.

There is no overarching explanation for Obama's successive Middle East failures, but there are a few factors worth considering: the increase in the number of asymmetrical conflicts, in which the traditional use of force is largely ineffective; increasingly blurred lines between difficult allies and intransigent adversaries; and major political differences between a centrist US president and a Congress that is dominated more than ever by extreme ideas.

But Obama himself bears a large part of the blame. Contrary to what one might think, he does not have a real strategic vision of the world - a shortcoming reflected in his quick capitulation in the face of opposition to his proposals. Obama often has a plan A, but never a plan B. When it comes to conducting a successful foreign policy, plan A is never enough.

Zaki Laidi is Professor of International Relations at Institut d'etudes politiques de Paris (Sciences-Po).