Japanese e-commerce giant Rakuten Group has returned to the U.S. junk bond market to shore up more cash for its struggling mobile unit and to help repay debt.

Amazon.com¡¯s competitor in Japan is looking to add on another $200 million (?26.4 billion) to a series of notes that it first sold last year, according to a person familiar with the matter. Rakuten tapped the market in November for $500 million at a whopping 12% yield. The Morgan Stanley-led offering is expected to price later in the week.

The firm¡¯s November transaction also went to funding capital investments for its mobile business and for the repayment of debt. In December, its ratings were cut further into junk by S&P Global Ratings.