turn on shell tracing of a makefile

hey, within a shell script file I know how to turn on tracing using "-x"
#!/bin/bash -x

now I have a complicated makefile which contains lots of `command`, and i would like to trace these `command`, where shall i put the option "-x"?

thanks!

make -d
will gives lots of debug information generated by `make`. however the variable expansion is not shown in the output.