Freddie Mac this week is offering to buy back from investors up to $30 billion principal amount of its debt to reduce its effective short-term debt, the second-largest U.S. home funding provider said on Monday.

The tender offer would be Freddie Mac's largest ever. It began on Monday and ends on Friday, unless it is extended.

The company is offering to buy back for cash various debt from issues totaling nearly $70 billion with maturities between September 2009 and August 2010.

We're buying back these contractually maturing securities, and over time we'll be issuing longer maturities, Mohit Sudhakar, senior director of debt portfolio management, told Reuters.

It's just a simple liability management trade, he said.

Freddie Mac's last dollar-denominated tender offer in 2006 was also its largest, in the mid-$20 billion area, Sudhakar said.

Barclays Capital is the lead deal manager for the offers, and Morgan Stanley and Deutsche Bank are deal managers, Freddie Mac said.