Ahead of the G20 summit meeting scheduled for April 2, the International Monetary Fund (IMF) criticized the U.S. and Treasury Secretary Tim Geithner, saying its plan to stabilize the financial system lacks essential details.

“Critical details concerning the valuation of distressed assets remain unclear,” says the IMF report. “The plan also does not address how severely undercapitalized or insolvent banks will be resolved?.?.?.?greater clarity on all these issues will be critical to ensure the plan’s effectiveness.”

The IMF forecasts the global economy will decline by 1% in 2009, its first contraction in 60 years and believes that the global economy is unlikely to turn round until governments achieve a “decisive breakthrough” in resolving the financial crisis.

“To break the negative feedback loop, it is extremely critical to resolve the uncertainty concerning the balance sheets of financial institutions,” it says. “Systematic and proactive approaches have started to supplant ad hoc interventions but financial sector policies still lack coherence and credibility. Greater international policy co-ordination is crucial for restoring market trust.”

The fund previously said that global governments should provide a total 2% of aggregate global GDP stimulus this year, and id recommending further boosts in 2010.

“Given the likely protracted nature of the downturn countries with fiscal room should plan to sustain stimulus in 2010.”

American Express could have its debt ratings cut by Standard & Poor’s on concerns that growing numbers of borrowers will default on their credit card debt.

“American Express has seen its asset quality deteriorate at a pace that exceeds median levels for the industry,” the rating agency said.

American Express this week said its net charge-off rate, debts companies believe they will never be able to collect, rose to 8.7% in February from 8.3% in January.

Amex said in a statement on its website that it was “disappointed” by the potential S&P move.

“We too are concerned about the impact of further deterioration in economic conditions going forward, but believe we have a number of strengths that position us well to navigate through this tough environment.”

Amex has raised rates for some 55% of its portfolio of credit card loans and closed inactive accounts in recent months to reduce the risk of default. Some cardholders have also been recently offered $300 each to pay off their balances and close their accounts.