Foreign assets held by Abu Dhabi's sovereign wealth fund are estimated to be at least $300bn, making it the second strongest rated in the world after Kuwait, Fitch Ratings has said. The rating agency said the emirate's $300bn assets compared to direct sovereign external debt of just $3bn after the maturing of a $1bn Eurobond earlier this year. The calculations come as Fitch affirmed Abu Dhabi's long-term foreign and local currency issuer default ratings at 'AA' with a stable outlook. It added that the emirate's foreign assets are estimated to have risen again in 2011, despite a dip in investment returns, as the general government budget moved further into surplus, despite a substantial spending increase. Sovereign net foreign assets held in Abu Dhabi total an estimated 131 percent of GDP at end-2011 and are second only to Kuwait's, Fitch said. The rating agency said Abu Dhabi Investment Authority's average return in the 20 years to 2011 dropped slightly to 6.9 percent from 7.6 percent in the 20 years to 2010.