Are AES-NI instructions supported in Red Hat Enterprise Linux 5?

Issue

GCC 4.4 in RHEL5.4 supports AES-NI but the assembler does not seem to recongnise the AES-NI instruction set.

    :157: Error: no such instruction: `aesimc 16(%rbx),%xmm0'
    :160: Error: no such instruction: `aesimc 32(%rbx),%xmm0'
    :164: Error: no such instruction: `aesimc 48(%rbx),%xmm0'
    :168: Error: no such instruction: `aesimc 64(%rbx),%xmm0'
    :172: Error: no such instruction: `aesimc 80(%rbx),%xmm0'
    :176: Error: no such instruction: `aesimc 96(%rbx),%xmm0'
    :180: Error: no such instruction: `aesimc 112(%rbx),%xmm0'
    :184: Error: no such instruction: `aesimc 128(%rbx),%xmm0'
    :188: Error: no such instruction: `aesimc 144(%rbx),%xmm0'
    :193: Error: no such instruction: `aesimc 160(%rbx),%xmm0'
    :198: Error: no such instruction: `aesimc 176(%rbx),%xmm0'
    :203: Error: no such instruction: `aesimc 192(%rbx),%xmm0'
    :209: Error: no such instruction: `aesimc 208(%rbx),%xmm0'