(Clarifies in paras 5-6 discussion over size of possible BNP Paribas fine)
LONDON, June 6 (Reuters) - The European Central Bank can still tweak some of its interest rates, although further cuts to its benchmark refinancing rate are unlikely, the bank's vice president said on Friday.
The ECB took the bold step of effectively charging banks if they park cash with it on Thursday by taking its marginal deposit rate - one of the two rates that straddle its benchmark refi rate - into negative territory.
"(ECB head Mario) Draghi made clear that for all practical purposes this is the lower bound, but he also didn't exclude that in some developments of the situation, we will act," Constancio said in an interview with CNBC.
"As he said, we can still act in some of the key rates... For instance we could tweak with the corridor, not necessarily the main refinancing rate."
In response to another question on the impact of a possible fine of "as much as 16 billion euros" by U.S. authorities on France's biggest bank BNP Paribas, Constancio said it would "not necessarily kill the bank".
Earlier, Reuters reported that U.S. authorities negotiating with BNP Paribas over alleged sanctions violations at one point suggested that it pay a penalty as high as $16 billion, not euros. ($1 = 0.7332 Euros) (Reporting by Marc Jones)