* Fed chair surprises markets with rate-rise scenario
* Fed trims monthly bond buying to $55 bln
* Yen drops against dollar by more than 1 percent
(New throughout, udpates prices and market activity, adds Yellen comments)
NEW YORK, March 19 (Reuters) - The dollar jumped on Wednesday as Federal Reserve Chair Janet Yellen surprised world markets by hinting that the central bank may accelerate the timetable for ending low U.S. interest rates.
The Japanese yen fell more than 1 percent against the dollar while the dollar index gained 0.7 percent to 79.38 after the Federal Reserve ended a two-day meeting by saying it would push ahead with plans to wind down its bond-buying stimulus.
The central bank also said it will likely need to keep interest rates low even after the economy recovers given lasting scars from the financial crisis.
But at a later news conference, Yellen said interest rates could start rising six months after the anticipated end this fall of the Fed's bond-buying program, now running at $55 billion monthly.
"It's a little bit more hawkish than people expected," said Shaun Osborne, foreign exchange strategist at TD Securities in Toronto. "They seem to see interest rates rising sooner rather than later. ... This is helping the dollar."
Ahead of the Fed policy statement, the dollar had been up against the yen and the euro but climbed sharply as Yellen spoke.
The dollar in late New York trade stood at 102.55 yen to the dollar, up 1.2 percent, and retraced some gains in early Asian currency trading.
The euro backed away from the $1.40 level it had been approaching and was at $1.3816 on Wednesday for a decline of 0.83 percent. It, too, reclaimed some losses in Asian trading.
The Swiss franc also dropped against the dollar and traded off 1.05 percent at 0.8820 francs to the dollar.
Sterling, which had come off a one-month low and risen as high as $1.6653, was also knocked down by the Fed news and was off 0.4 percent at $1.6527 in late New York trade.
Sterling had risen with help from British data showing wages ticking higher and a steadily improving jobs market. The number of Britons claiming jobless benefits fell more than expected while wages rose 1.4 percent year-on-year, which though higher than forecast was still below inflation.
Investors remained cautious over tensions in Ukraine. Anxiety eased somewhat after Russian President Vladimir Putin said on Tuesday he did not plan to seize other regions of Ukraine after Crimean citizens on Sunday voted to be annexed by Moscow.
(Additional reporting by Anirban Nag in London; Editing by James Dalgleish and David Gregorio)