That came as the dollar strengthened against the euro ahead of Yellen's speech at the Jackson Hole Symposium on this week: the greenback was up 0.5 per cent against the euro at €0.8892 in late afternoon in London.
Markets are expected to pay close attention to her speech - so far, the consensus is for a hawkish tone.
"While the message coming from Fed officials has been quite mixed and left the markets with little idea of what the Fed is planning – it initially intended to raise rates four times this year and so far it hasn’t done so once – the message from Stanley Fischer and William Dudley, both permanent voters on the Federal Open Markets Committee, last week were quite hawkish," pointed out Craig Erlam, senior markets analyst at Oanda.
"Should Yellen deliver an equally hawkish warning on Friday then I expect markets to respond accordingly, with December likely becoming the most likely meeting but September being more priced in that it currently is.
"Equally, should she keep the cards close to her chest as she has opted to in the past, markets may take this as a sign that she is still far from convinced and could push back rate expectations even further. Given the situation we find ourselves in, it’s perhaps not entirely surprising that we’re seeing this cautious approach this week, particularly in such illiquid summer markets."
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