The new era of relations between China and the US promised when Xi Jinping and Barack Obama met in California last June has yet to materialise. Ties have cooled over tensions arising from rivalry, cyber issues, military operations, alliances and territorial disputes. The presidents have to be on better terms if there is to be a chance of building a new type of major power relationship. There is hope of that this month when first ladies Peng Liyuan and Michelle Obama meet in Beijing while their husbands talk in the Netherlands. Peng and Michelle Obama are highly popular at home, their glamour and fashion sense giving them superstar appeal. Each made the latest Forbes list of the world's 100 most powerful women. They have common interests in education and health programmes, promoting their causes internationally. There are no better ambassadors for Sino-US soft power. They were first expected to meet in California, but Michelle Obama did not go due to family commitments. While understandable from an American point of view, it was perplexing in a diplomatic context. Xi and Barack Obama have since only spoken by phone, but they will meet on the sidelines of the March 24-25 Nuclear Security Summit in The Hague and will likely hold talks at the Asia-Pacific Economic Co-operation Forum in Beijing in November. The quality of their dialogue would be substantively raised were their wives to partner on shared issues. By simply appearing together, the two women could project a more positive face of Sino-US relations ties. But the benefits would run far deeper were they to bond and form a friendship. Partnering on common goals, such as the international fight against HIV-Aids and tuberculosis - for which Peng serves as a World Health Organisation ambassador - would also be of global benefit. Working together would send the clearest of messages to their husbands and offer a chance to build trust and co-operation at the uppermost level of relations. The wives of previous Chinese leaders were almost invisible; Peng's star qualities give her global appeal. The opportunity afforded by Michelle Obama's week-long trip with her two daughters and mother starting tomorrow is unprecedented. Her non-political focus deviates from immediate predecessors Laura Bush and Hillary Rodham Clinton. A friendly bonding of Peng and Michelle Obama could give Sino-US relations the warmer and more positive tone that is so badly needed.