If you are a green card holder, you are automatically classified as a United States tax resident and must report all of your income, whether earned abroad or domestically.Please see below:
Publication 4588 (02-2007)Basic Tax Guide for Green Card Holders: Understanding Your U.S. Tax Obligations
There is a common rumor circulating that the number of days you spend within the United States decides whether or not you are considered to be a tax resident, but this is only true for people who are in the country under nonimmigrant visas, not green cards. If you have a green card and you do not step foot in the United States all year, you still must report all of your income to the IRS.
Like almost every other taxpayer in the United States, green card holders must file an IRS Form 1040 each year by April 15th. If you fail to file your United States taxes as a green card holder, you may hurt your chances of becoming a U.S. citizen. Additionally, if you intentionally do not file your taxes, you may also be guilty of a crime which could result in the loss of your green and your deportation. You should be able to find out more about your situation by visiting the IRS website at www.irs.gov.
If you pay tax to the Ethiopian Government on the same money that you pay tax to the IRS on, you may claim a credit for the foreign tax paid by filing Form 1116Foreign Tax Credit
I hope this helps
I did not accept your answer because you did not consider important parameters I gave you inmy question. You only saw the fact that I am a none US citizen and a green card holder. The other important parameter that you seem to forget in your analysis is that I am an employee of the World Bank. Just like UN staff, World Bank employees are exempted from taxes.
Please see what the tax desk in the World Bank wrote me below.
"Consultant income earned by non-US citizen (green card holders included) staff is not subject to US income tax and social security tax. As long as you are not US citizen, the consultant you earn from the World Bank will not be subject to US income taxes. Therefore, we will NOT be reporting your Bank's income to the IRS nor will you be required to report/pay on this income to the IRS (via 1040 filing). Any other income you earned (interest, wages) you received OUTSIDE your STC appointment with the Bank may be subject to tax. Below is the non-US Memorandum including the IRS Publication 519 referencing Employees of Foreign Governments and International Organizations. I hope this helps.