US Secretary of State Hillary Clinton has said she will step down as America's top diplomat and enjoy some rest despite the re-election of Barack Obama as US president. Though many see this as the end of her political career, her diplomatic legacy will continue to exert influence across the world.

Since becoming the secretary of state in 2009, Clinton has made 70 overseas trips to more than 100 countries, spent 340 days on the road, including more than 80 days on her Air Force 757, and has been praised by the American media as a diplomatic "labor model".

Clinton has brought great strategic thinking to her job. Despite a mountain of domestic economic problems created by the global financial crisis, solving the diplomatic problems left behind by former US president George W. Bush was once high on her diplomatic agenda. According to American media reports, Clinton has worked into the small hours in her office trying to find ways to retain the US' global leadership and rebuild its credibility, and to deal with various global challenges in the post-Cold War era.

She is an advocate of the art of smart power and has peddled a flexible foreign policy philosophy around the world in a steadfast and composed way, which has improved Washington's image in the international community.

Soon after assuming office, Clinton began to reshape the US' relations with China and other emerging powers. Though she said the US was looking for ways to support China's peaceful rise, she mixed it with some tough rhetoric on China.

Most of all, she has spared no efforts in promoting Obama's "pivot to Asia" strategy. She visited the Association of Southeast Asian Nations secretariat in Jakarta, Indonesia, in February 2009 and stressed the importance of the region for the US, signaling the beginning of the "pivot to Asia" strategy.

The same year, she signed the US Instrument of Accession to the Treaty of Amity and Cooperation in Southeast Asia at the ASEAN ministerial meeting in Thailand, something ASEAN had been seeking for 17 years, and agreed to the first ASEAN-US summit.

Improvement in relations with Myanmar is a breakthrough in the US' strategy for the region. For decades, the US had been hostile toward Myanmar and imposed sanctions on it. But Clinton has said publicly that the US will review its policy toward Myanmar, shifting from sanctions to engagement.

These are considered strategically important diplomatic decisions to further strengthen the US' ties in Southeast Asia.

After his re-election, Obama's first overseas trip was to Myanmar, Thailand and Cambodia. The US president's visit to Myanmar filled a geographical gap in Washington's "return to Asia" strategy. The US' "pivot to Asia", now called Asia-Pacific "rebalancing", will undoubtedly be Obama's diplomatic legacy with Hillary as its main promoter.

The US' strategic "rebalancing" toward East Asia, coupled with its intensifying military presence in the region, is considered an important strategy to contain China and has raised the hackles of Chinese strategists. The US' involvement in the South China Sea and the Diaoyu Islands dispute has exacerbated China's concerns that the US is trying to encircle China. This in turn has intensified bilateral strategic distrust and tensions.

China's peaceful rise has prompted Washington to make Beijing the most prominent target of its global strategy, and one of the principal aims of the US' strategic rebalancing is to contain China's rise.