President Reagan today dedicated the next flight of the American space shuttle to anti-Soviet insurgents in Afghanistan and promised to keep a spotlight on Kremlin intervention in that country.

''We cannot and will not turn our backs on this struggle,'' he said as he signed a joint resolution passed by Congress condemning the Soviet Union for its role in Afghanistan.

The resolution was conceived by the European Parliament, whose Vice President, Egon Klepsch of West Germany, also spoke at today's ceremony. Soviet forces entered Afghanistan in December 1979 and still occupy the country.

The re-usable shuttle's third flight is scheduled to begin March 22 and Mr. Reagan dedicated it to insurgents fighting Soviet and Afghan Army troops.