In the field of disarmament, Obama delivered a utopian "nuclear-free world" speech in Prague in April, urging all countries to abandon Cold War mentality and reduce nuclear weapons. The US pushed the UN Security Council to organize a nuclear disarmament and nuclear non-proliferation summit, too, which certainly is a meaningful endeavor. Likewise, the US has assumed a responsible role in shaping a new global climate political mechanism.

In other words, the abyss US diplomacy had fallen into during the Bush administration is evident to everyone. But despite being more successful in dealing with world affairs, compared to solving problems at home, Obama still faces a series of knotty questions.

His effort to clear the mess America has created in the Middle East in the name of counter-terrorism by waging a war against the Taliban has worsened the situation in Afghanistan. Obama announced his "new Afghanistan strategy" on Dec 3, ordering an increase of 30,000 US troops over 18 months. But it is open to debate whether his new strategy for Afghanistan will work. In fact, a new wave of terrorist attacks this year has already forced his administration to consider opening a new counter-terrorist front in Yemen.

Though the US has extended its hand to Iran and the DPRK with the hope of the resolving intractable nuclear issues, mutual doubts still remain. That the two countries have not yet responded positively to America's overtures shows they still pose a potential threat to US interests.

Relations among major global powers are yet to take the direction in America's favor, as Obama expected them to, and US-Russian ties have improved only to a limited degree. Moreover, the time-honored ties between the US and Japan are also facing difficulties.

In Sino-US relations, the Taiwan issue and human rights have always been sticking points. But now, trade disputes could complicate matters further.

It is doubtful, too, whether Obama's efforts to mitigate climate change will get the US Senate's approval.

The transformation of the international order reflects the decline of America's comparative advantage and ebbing of its international influence. Though Obama has shown an unswerving resolve to adapt to changing reality, his serious-minded philosophy lacks enough steam to lift the US to its position in the 1990s.

The nagging problems at home are acting as brakes for Obama's aggressive diplomatic ambitions, making America's pursuit of the strategic targets of hegemony a turbulent affair. In this sense, Obama's new political and diplomatic doctrine appears more like strategic adjustment than a prescription to arrest the decline of America hegemony.

The author is director of the Institute of America Studies, Chinese Institute of Contemporary International Relations.