diff --git a/openmp/libomptarget/DeviceRTL/include/Interface.h b/openmp/libomptarget/DeviceRTL/include/Interface.h
--- a/openmp/libomptarget/DeviceRTL/include/Interface.h
+++ b/openmp/libomptarget/DeviceRTL/include/Interface.h
@@ -198,6 +198,9 @@
 /// Called by the worker threads in the parallel region (function).
 void __kmpc_get_shared_variables(void ***GlobalArgs);
 
+/// External interface to get the thread ID.
+uint32_t __kmpc_get_hardware_thread_id_in_block();
+
 /// Kernel
 ///
 ///{
diff --git a/openmp/libomptarget/DeviceRTL/src/Mapping.cpp b/openmp/libomptarget/DeviceRTL/src/Mapping.cpp
--- a/openmp/libomptarget/DeviceRTL/src/Mapping.cpp
+++ b/openmp/libomptarget/DeviceRTL/src/Mapping.cpp
@@ -226,4 +226,9 @@
 bool mapping::isGenericMode() { return !isSPMDMode(); }
 ///}
 
+extern "C" {
+uint32_t __kmpc_get_hardware_thread_id_in_block() {
+  return mapping::getThreadIdInBlock();
+}
+}
 #pragma omp end declare target