You will need to fill out Form 1116 - Foreign Tax Credits which will offset your US tax obligation dollar for dollar. You convert the foreign taxes you paid to USD first.
But, are you living in the foreign country, or in the USA? Most tax treaties say that the country of residence is where you owe the taxes, even on the foreign country social security pension.
As an example: I used to live in Switzerland, and when living there I paid tax there on my Swiss Social Security and Swiss Company Pension, also US Social Security. When I filed US taxes I took foreign tax credits.
Now I live in the USA and Switzerland no longer taxes me on any of my Swiss based income. Now I claim it as "Other Income" and pay US taxes only and do not need to deal with Form 1116 complications. Note, that I had to maintain documentation on the cost basis of my company pension there as I had paid US taxes on the contributions each year. I only enter the taxable portion in Other income.
