Stock markets across Asia were flat on Wednesday (29 March) as the UK prepares to formally begin the process of exiting the European Union.

Prime Minister Theresa May signed a letter to trigger Article 50 of the Lisbon Treaty, which will be delivered to European Council president Donald Tusk at 12.30 BST.

Tokyo's benchmark Nikkei share average edged down 0.1% to 19,186.10 points at mid-day after official data showed Japanese retail sales increased a less-than-expected 0.2% in February.

The Shanghai Composite index was up 0.1% at 3,257.66 while Hong Kong's Hang Seng benchmark also advanced 0.1% to 24,376.49.

The pound fell 0.3% against the US dollar as investors fretted over the potential effects of Brexit on the UK economy.

US markets staged a rebound overnight after a measure of American consumer confidence rose to its highest level in 16 years in March. The Dow Jones and S&P 500 share averages both closed 0.7% higher.

Analysts said the start of the Brexit process had already been priced in by markets in the US and that Wall Street was more concerned with whether President Donald Trump can bounce back from his failure to repeal and replace Obamacare.

"I think this was a turnaround Tuesday and we'll wait and see," Art Cashin, director of floor operations at UBS, told CNBC.

"The market wants it to look like [the White House] is getting something done. People are pushing for [Trump] to get off taxes and do infrastructure."

Andrew Brenner, global head of emerging market fixed income at National Alliance, added: "I'll be watching Brexit but I don't think it's going to have much effect. I think the negotiations will be going on for two years."

Elsewhere, Australia's S&P/ASX 200 index advanced 0.9% to 5,873.50 points, led by gains in the mining, banking and energy sectors.

In Seoul, the Kospi benchmark was unchanged at 2,163.60.