Keller-Sutter, who said she held a Credit Suisse bank account, said the worst case had been avoided.
"This is no bailout. This is a commercial solution because UBS is taking over Credit Suisse," she told a press conference in Bern.
"The bankruptcy of Credit Suisse would have had a huge collateral damage - on the Swiss financial market also internationally," she said.
She said she had been in contact with "colleagues from the UK and USA" who were "very grateful for this solution because they really feared that there could be a bankruptcy of Credit Suisse with all the losses."
Swiss National Bank Chairman Thomas Jordan said it was vital that a solution had been found quickly. The central bank helped by providing 100 billion Swiss francs ($108 billion) in liquidity assistance.
"Credit Suisse is classified as a global systemically important bank due to its size and global network," he told reporters. "The solution we have now ensures that the systemically important function remains secure."
UBS Chairman Colm Kelleher, who will lead the combined entity as chairman, described the deal as a great opportunity, although there was lots of work to do.
"We will be de-risking a lot of those tricky businesses that we are inheriting from Credit Suisse," he told reporters.
He said it was far too early to discuss job cuts at Credit Suisse, but he was very positive about Credit Suisse's Swiss business.
"It is a fine asset that we are very determined to keep," Kelleher said.
His upbeat tone contrasted with Credit Suisse Chairman Axel Lehmann, who was emotional when he spoke about the demise of 167-year-old Credit Suisse as an independent bank.
"Today is a historic, sad and very challenging day," he said.
The bank had been caught by old burdens which had materialised, he said.
"It's an accumulation of things that have built up over many, many years, and, in total, the barrel has burst," Lehmann said.
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