Blackstone raised $9 bln so far for fund-source

* Blackstone raised about $9 bln for fund-letter

* Aims to finish fundraising end of Q2-letter

NEW YORK Jan 13 (Reuters) - Private equity giant Blackstone Group (BX.N) has raised about $9 billion so far for its sixth global buyout fund and is aiming to complete fundraising at the end of June, it told investors in a recent letter.

Blackstone began raising the fund, BCP VI, about two years ago.

That has become an increasingly tough period to ask investors for cash. Pension and endowment investors, which took a large hit on their equity portfolios during the financial turmoil, have been unwilling to commit fresh capital.

Recent research from London-based firm Preqin said private equity fundraising slumped to its lowest level in five years in 2009.

Blackstone did not publicly disclose a target when it started raising the fund, although research from Preqin dated 2008 put the target at $20 billion.

Blackstone has more recently said it aimed to raise a number in the low to mid teens.

The company has a vast amount of "dry powder" -- capital available for investment -- from previous funds raised. It said in November it has $27 billion of dry powder, the lion's share of which is in its real estate and private equity funds.

Details of the letter were disclosed to Reuters by a source who has read the document.

Blackstone declined comment. (Reporting by Megan Davies)