* U.S. Treasury yields up 25 bps from Sept. 8 lows
* Euro posts first monthly loss in seven months
* Graphic: World FX rates in 2017 http://tmsnrt.rs/2egbfVh
LONDON, Sept 29 (Reuters) - The dollar is on track to post its best weekly performance so far this year as a bounce in U.S. Treasury yields fueled by the Trump administration's tax plan triggered a shake out in multi-year short bets against the greenback.
While market watchers remain sceptical about the dollar's long-term outlook, citing the long time it will take for the tax plan to become legislation, the greenback has punched above some key levels this week.
"We need to see more clarity on the data front and the progress of the U.S. tax plan through Congress before we become bullish on the dollar," said Thu Lan Nguyen, an FX strategist at Commerzbank AG in London.
The dollar index, a trade-weighted basket of the greenback against its rivals, was broadly flat at 93.12. It has gained more than 1 percent this week, putting it on track for its best weekly performance since December.
President Donald Trump offered a plan on Wednesday that calls for lower tax rates for businesses and individuals as part of a comprehensive overhaul of the U.S. tax code.
Data in the coming days will provide further evidence on the health of the U.S. economy.
Investors will turn their focus to U.S. economic data, including the personal consumption expenditures (PCE) price index for August later in the day followed by the U.S. jobs data due on Oct. 6.
Traders said the dollar rally may have further legs for now as the technical picture is supportive on the bond markets.
At the peak of the Trump fiscal policy reform expectations earlier this year, 10-year U.S. Treasury yields had risen above 2.60 percent.
Despite this month's rise of a quarter percentage point from the Sept. 8 lows, ten-year yields remain at 2.31 percent.
Elsewhere, the euro nursed losses and is poised for its first monthly decline since February this year as the results of German elections prompted some profit-taking into a double-digit rally in the single currency this year.
The single currency was flat at $1.1791 and has fallen nearly a percent so far this month.
Euro zone inflation data is the key event risk for currency markets with inflation in the 19-country currency bloc expected at 1.6 percent for September compared with 1.5 percent in August. The ECB targets inflation at just below 2 percent.
For Reuters Live Markets blog on European and UK stock markets see reuters://realtime/verb=Open/url=http://emea1.apps.cp.extranet.thomsonreuters.bi z / c m s / ? p a g e I d = l i v e m a r k e t s (Reporting by Saikat Chatterjee, editing by Larry King)