Opinion | Apec agreements help warm the world's most important bilateral relationship

Unexpected twists in Sino-US relations were the highlight of last week's Apec summit in Beijing. Ties between the two nations warmed during the meeting as the two heads of state, Barack Obama and Xi Jinping, held candid talks.

The good news kept coming: China and the US agreed to clear tariff barriers for hi-tech products; there was a breakthrough in their 17-year negotiations on an IT agreement; and they committed to reducing greenhouse gases over the next 15 to 20 years. They also said they would extend business, tourist and student visas, while agreeing to increase mutual trust between their armed forces.

Yet such achievements did not come easily. Last year's meeting between Obama and Xi in California created a positive atmosphere, but the momentum did not last. Relations over the past year had worsened, mainly over Pacific Rim conflicts. So there were few expectations before the summit.

Xi and Obama's comments at the Apec summit show that both view Sino-US relations as very important for a peaceful, stable and prosperous Asia-Pacific region, and world. If China and the US do not work together, it may be difficult to find definitive solutions to many of today's global problems.

Their deal to cut emissions is an example of win-win cooperation, given that together the US and China produce 40 per cent of global carbon emissions. Even though China, as a developing country, strongly supports the principle of "common but differentiated responsibilities" - in which the obligation is mainly on developed nations to cut emissions - it realises it has to commit to reductions too, given the scourge of pollution at home. This is also a path to sustainable development.

The US, for its part, has been under fire for years over its lack of commitment to fighting climate change, in particular its refusal to sign the Kyoto Protocol. Xi and Obama's Apec emissions deal showcases not only their leadership abilities, but also the image of China and the US as responsible global powers. This deal may be instrumental in the signing of the UN agreement on climate change in Paris next year.

Some people on both sides of the Pacific remain pessimistic about Sino-US relations. In the past year, ties have often been at a low ebb, while Sino-Russian relations have hit new highs.