Invesco's (NYSE:

) PowerShares unit has become the latest ETF issuer to make its presence felt in the broadening ETF cost battle by announcing significant fee reductions on six of its funds. PowerShares, the fourth-largest U.S. issuer, said it has lowered the annual expense ratio on the $285.7 million PowerShares FTSE RAFI Developed Markets ex-U.S. Portfolio (NYSE:

) to 0.45 percent from 0.75 percent. The The PowerShares FTSE RAFI Emerging Markets Portfolio (NYSE:

), which has $350.2 million in assets under management, has a new expense ratio of 0.49 percent compared with a previous rate of 0.85 percent. The The PowerShares FTSE RAFI Asia Pacific ex-Japan Portfolio (NYSE:

) and the PowerShares FTSE RAFI Developed Markets ex-U.S. Small-Mid Portfolio (NYSE:

) have seen fee reductions to 0.49 percent from 0.8 percent and 0.75 percent, respectively. The PowerShares S&P International Developed High Quality Portfolio (NYSE:

) is now home to annual fees of 0.45 percent, down from 0.75 percent. PowerShares also pared the fees on the PowerShares S&P 500 High Quality Portfolio (NYSE:

) to 0.29 percent from 0.5 percent. All of the fee cuts went into effect on November 21. "We continuously analyze ways to improve our overall ETF product lineup for investors," said Ben Fulton, Invesco PowerShares managing director of global ETFs, in a statement. "We believe the lower fees announced today better align the six funds with our existing offerings, and help position the PowerShares family of ETFs for continued growth." With the announcement, PowerShares becomes the latest major ETF sponsor to pare expenses charged to investors. Over the past year, Charles Schwab (NYSE:

), State Street's (NYSE:

) State Street Global Advisors unit and Vanguard cut fees on some of their ETFs. In September, BlackRock's (NYSE:

) iShares fired back by announcing

. Last month, iShares unveiled its core suite of ETFs

. PowerShares had $70.5 billion in AUM as of November 26,

. The firm has more than double the ETF assets of the fifth-largest U.S. ETF sponsor. For more on ETFs, click

.