U.S. President Barack Obama on Tuesday nudged Chinese President Hu Jintao to allow the yuan currency to appreciate at a landmark summit in Beijing. 

Obama referred fleetingly to the issue which has spawned testy exchanges between Chinese and U.S. officials, who argue that an undervalued yuan is stoking global economic imbalances.

The yuan has been effectively pegged against the dollar since the middle of last year.

Here is an overview of key comments on the yuan this year.

Jan 22, 2009 - Obama believes China is manipulating its currency, Timothy Geithner, Obama's choice to head the U.S. Treasury says in written Congressional testimony, using a term the Bush administration avoided for years to describe Beijing's foreign exchange practices. [ID:nN22364222]

-- Officials later put the choice of words down to sloppy staff work, however, not a change of policy.

April 15 - Treasury report declines to name China a currency manipulator. It says the yuan is undervalued, but that Beijing's practices do not fit its legal definition of currency manipulation. 

April 16 - U.S. senator Debbie Stabenow says she will introduce legislation directing the Commerce Department to determine whether a country's currency is fundamentally misaligned. 

June 8 - World Bank chief Robert Zoellick welcomes China's efforts to make its currency more international. Warns against abrupt, unilateral moves that could worsen the fragile global financial situation. 

Sept 15 - The yuan will be increasingly recognised as a global currency as its economy develops, says senior central bank official Liu Guangxi. 

-- On the same day, Guo Qingping, an assistant People's Bank of China governor, says China will proceed cautiously in promoting the yuan as an international currency. 

Oct 3 - China will stick to its current exchange rate policy and aim to maintain market stability, Yi Gang, a central bank vice governor, says at an IMF meeting in Turkey. 

Oct 27 - The United States welcomes the rise in the yuan in recent years but wants the currency to climb further, Commerce Secretary Gary Locke says in Guangzhou.

Nov 5 - The yuan's de facto peg to the dollar is unsustainable in the long run, but Chinese academics are deeply divided on what should replace it, one of China's leading government researchers says.

-- On the same day, European Central Bank President Jean-Claude Trichet says that a steady rise of China's yuan currency would help rebalance the world economy. 

Nov 6 - Japan's deputy finance minister, Yoshihiko Noda, calls on China to free up the yuan. 

Nov 9 - Obama tells Reuters he plans to raise the issue of the yuan currency when he visits China.

Nov 10 - Foreign Ministry spokesman Qin Gang restates China's long-standing policy to maintain the basic stability of the yuan at a reasonable and balanced level.

Nov 11 - In Singapore, World Bank Chief Zoellick calls the dollar's role as a reserve currency relatively secure, but says over the next 10-15 years the renminbi will provide an alternative once it is internationalised. 

-- The same day, China sends its clearest signal yet that it is ready to allow yuan appreciation after an 18-month hiatus, saying it will consider major currencies, not just the dollar, in guiding the exchange rate. 

Nov 13 - The head of the world's most valuable bank by market capitalisation, Industrial & Commercial Bank of China, says a stronger yuan will not be conducive for global economic recovery. 

Nov 14 - Morgan Stanley Asia Chairman Stephen Roach says China may let its yuan currency rise gradually, once the economic recovery becomes sustainable. 

Nov 15 - China's Vice Commerce Minister Chen Jian plays down talk of a shift in central bank currency policy and mounting expectations of a rise in the yuan exchange rate. 

Nov 16 - Dominique Strauss-Kahn, IMF managing director, says a stronger yuan is part of the policy mix Beijing needs to boost domestic consumption, and ease global imbalances. 

-- China's Commerce Ministry rebuffs calls for the yuan to appreciate. Yao Jian, ministry spokesman, says the goal is to provide a stable and predictable environment for enterprises.

-- On the same day, U.S. Commerce Secretary Gary Locke says China has made progress, but needs to do more to raise the value of its currency.

Nov 17 - U.S. President Barack Obama nudges Chinese President Hu Jintao to allow the yuan to appreciate at meeting in Beijing.

-- Hu does not mention the yuan, China's currency policy or the dollar during remarks following the meeting.

-- The IMF's Strauss-Kahn also repeats his position from the day before, saying The sooner the better in response to a question on when the yuan should rise.