LONDON, Dec 8 (Reuters) - The United States became Britain"s biggest export market for financial services in the run up to Brexit, overtaking the European Union where sales shrank in 2020, TheCityUK lobby group said on Wednesday. Britain"s financial sector was largely cut off from the EU - previously its single biggest customer - when Britain fully left the bloc"s orbit last December. For 2020, total financial services exports remained little changed at 82.4 billion pounds ($109.07 billion). Exports to the EU fell 6.6% to 24.7 billion pounds, but rose 4.1% to 57.7 billion pounds to non-EU countries. Exports to the United States rose 5.3%, said TheCityUK, which promotes Britain"s financial sector overseas. Britain"s financial services trade surplus of $80.6 billion remains the largest in the world, nearly the same as the next two leading countries, the United States and Singapore, combined at $91.7 billion. The EU, meanwhile, is building up its autonomy in finance, making it unlikely that Britain will regain unfettered access to the continent"s investors and financial markets. The UK’s status as a world leading financial centre is at risk unless industry, government and regulators work together to boost long term competitiveness, deepen key trade links, and focus on new areas of future global growth," said Anjalika Bardalai, TheCityUK"s chief economist and head of research. Britain is now revising its financial rules to maintain London"s attractiveness as a global financial centre to keep up with leader New York, and fend off competition from EU cities like Amsterdam as well as Asian centres. ($1 = 0.7555 pounds)