(Updates prices, adds comments; changes byline, dateline, pvs LONDON)
* Euro retreats from 5-1/2-month high
* Dollar hits nearly 4-week high vs yen
* Eyes on Trump announcement on tax reform
* Aussie, kiwi big losers after Australian inflation data
* Graphic: World FX rates in 2017 tmsnrt.rs/2egbfVh
By Sam Forgione
NEW YORK, April 26 (Reuters) - The U.S. dollar strengthened broadly on Wednesday, with the currency hitting nearly four-week highs against the yen, on anticipation that a promised White House announcement on tax reform could boost the greenback.
The dollar jumped to 111.73 yen, its highest level so far this month, while the euro was last down 0.5 percent against the greenback at $1.0874 after touching a 5-1/2-month high of $1.0950 on Tuesday ahead of the tax plan announcement. The euro rose to match that same high against the dollar in early trading on Wednesday.
U.S. Treasury Secretary Steve Mnuchin said the plan for "the biggest tax cut" in U.S. history due to be released later on Wednesday would cut the business tax rate to 15 percent, including for small businesses.
Analysts said traders were also taking profit on bearish "short" bets against the dollar and bullish "long" bets on the euro after the dollar had plunged against the euro in recent days following centrist Emmanuel Macron's victory against anti-euro nationalist Marine Le Pen in the first round of France's presidential elections.
Gains for the euro this week have also been spurred by expectations of a change in the direction of European Central Bank policy in coming months. The ECB is set to meet on Thursday.
"The dollar is seeing some strength across the board today on excitement and expectations for the Trump tax plan," said Douglas Borthwick, managing director at Chapdelaine Foreign Exchange in New York.
Borthwick said, however, that traders' skepticism that any announced plan would pass through the U.S. House and Senate exactly as proposed capped the dollar's gains.
The Australian dollar sank about 1 percent against the greenback to a more than three-month low of $0.7462 after soft Australian inflation numbers.
Key measures of core inflation stayed stubbornly short of the Reserve Bank of Australia's (RBA) 2 to 3 percent target band, implying there was scant pressure for a hike in interest rates anytime soon.
The data also hurt the Aussie since it increased the chance that the RBA could lower interest rates again, said Richard Scalone, co-head of foreign exchange at TJM Brokerage in Chicago.
The New Zealand dollar also tumbled about 1 percent against the U.S. dollar, hitting its lowest level of the year at $0.6881.
The dollar index, which measures the greenback against a basket of six major rivals, was last up 0.4 percent at 99.171 .
Reporting by Sam Forgione; Additional reporting by Patrick Graham in London; Editing by Meredith Mazzilli