Singapore's domestic retail banks have struck an exceedingly cautious tone on allowing foreign rivals access to their cash-machine networks ahead of talks expected when a landmark free-trade agreement is finalised. United States Trade Representative Robert Zoellick this month said that US banks would be allowed to negotiate access to local cash networks as part of a soon to be completed trade deal. The three domestic banks - United Overseas Bank (UOB), Oversea-Chinese Banking Corporation (OCBC) and DBS Group - have zealously guarded their two networks from foreign participation. The six foreign banks, which have restricted access to the retail market, have instead set up their own, limited networks, some of which are linked. Of the six, only one - Citibank, a unit of Citigroup - is a US-based lender. But analysts say that securing access for Citibank and others to the more extensive domestic cash-vending networks will help to level the playing field and complement other recent moves to liberalise the sector. An official with UOB, which runs an ATM network with rival OCBC, said that the infrastructure was regarded as one of their crown jewels. 'Any access to this distribution network will have to be evaluated very carefully,' said Sim Puay Suang, executive vice-president of personal financial services at UOB. OCBC also took a guarded line. 'We are open to having talks with the foreign banks but, obviously, any decision will have to be mutually beneficial,' an official said. State-linked DBS Group, which runs a separate ATM network with subsidiary POSBank, did not comment. The sensitivity of the topic was made clear in comments from Deputy Prime Minister Lee Hsien Loong who also heads the Monetary Authority of Singapore. Last year, Mr Lee described liberalisation of the ATM network as the local lenders' greatest concern. 'Because once you open up the ATM network, then straightaway, a foreign bank can have 1,000 points of access, which will be a very big change.'