diff --git a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/v1/Publisher.java b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/v1/Publisher.java
index efaba6cf1..9a1898e1e 100644
--- a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/v1/Publisher.java
+++ b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/v1/Publisher.java
@@ -36,13 +36,17 @@
 import com.google.api.gax.core.FixedExecutorProvider;
 import com.google.api.gax.core.InstantiatingExecutorProvider;
 import com.google.api.gax.grpc.GrpcCallContext;
+import com.google.api.gax.httpjson.HttpJsonCallContext;
+import com.google.api.gax.httpjson.InstantiatingHttpJsonChannelProvider;
 import com.google.api.gax.retrying.RetrySettings;
+import com.google.api.gax.rpc.ApiCallContext;
 import com.google.api.gax.rpc.HeaderProvider;
 import com.google.api.gax.rpc.NoHeaderProvider;
 import com.google.api.gax.rpc.StatusCode;
 import com.google.api.gax.rpc.TransportChannelProvider;
 import com.google.auth.oauth2.GoogleCredentials;
 import com.google.cloud.pubsub.v1.stub.GrpcPublisherStub;
+import com.google.cloud.pubsub.v1.stub.HttpJsonPublisherStub;
 import com.google.cloud.pubsub.v1.stub.PublisherStub;
 import com.google.cloud.pubsub.v1.stub.PublisherStubSettings;
 import com.google.common.base.Preconditions;
@@ -120,9 +124,10 @@ public class Publisher implements PublisherInterface {
 
   private final boolean enableCompression;
   private final long compressionBytesThreshold;
+  private final boolean enableRESTJsonTransport;
 
-  private final GrpcCallContext publishContext;
-  private final GrpcCallContext publishContextWithCompression;
+  private final ApiCallContext publishContext;
+  private final ApiCallContext publishContextWithCompression;
 
   /** The maximum number of messages in one request. Defined by the API. */
   public static long getApiMaxRequestElementCount() {
@@ -152,6 +157,8 @@ private Publisher(Builder builder) throws IOException {
     this.messageTransform = builder.messageTransform;
     this.enableCompression = builder.enableCompression;
     this.compressionBytesThreshold = builder.compressionBytesThreshold;
+    this.enableRESTJsonTransport =
+        builder.channelProvider instanceof InstantiatingHttpJsonChannelProvider;
 
     messagesBatches = new HashMap<>();
     messagesBatchLock = new ReentrantLock();
@@ -199,15 +206,24 @@ private Publisher(Builder builder) throws IOException {
             StatusCode.Code.UNAVAILABLE)
         .setRetrySettings(retrySettingsBuilder.build())
         .setBatchingSettings(BatchingSettings.newBuilder().setIsEnabled(false).build());
-    this.publisherStub = GrpcPublisherStub.create(stubSettings.build());
+    this.publisherStub =
+        this.enableRESTJsonTransport
+            ? HttpJsonPublisherStub.create(stubSettings.build())
+            : GrpcPublisherStub.create(stubSettings.build());
     backgroundResourceList.add(publisherStub);
     backgroundResources = new BackgroundResourceAggregation(backgroundResourceList);
     shutdown = new AtomicBoolean(false);
     messagesWaiter = new Waiter();
-    this.publishContext = GrpcCallContext.createDefault();
+    this.publishContext =
+        this.enableRESTJsonTransport
+            ? HttpJsonCallContext.createDefault()
+            : GrpcCallContext.createDefault();
     this.publishContextWithCompression =
-        GrpcCallContext.createDefault()
-            .withCallOptions(CallOptions.DEFAULT.withCompression(GZIP_COMPRESSION));
+        this.enableRESTJsonTransport
+            ? this.publishContext
+            : // TODO
+            GrpcCallContext.createDefault()
+                .withCallOptions(CallOptions.DEFAULT.withCompression(GZIP_COMPRESSION));
   }
 
   /** Topic which the publisher publishes to. */
@@ -448,7 +464,7 @@ private void publishAllWithoutInflightForKey(final String orderingKey) {
   }
 
   private ApiFuture<PublishResponse> publishCall(OutstandingBatch outstandingBatch) {
-    GrpcCallContext context = publishContext;
+    ApiCallContext context = publishContext;
     if (enableCompression && outstandingBatch.batchSizeBytes >= compressionBytesThreshold) {
       context = publishContextWithCompression;
     }