I can't use fetch in workers

interface Env {
  MY_BUCKET: R2Bucket;
  CREATOR: DurableObjectNamespace<CreatorDO>
}

export class CreatorDO extends DurableObject {
  constructor(ctx: DurableObjectState, env: Env) {
    super(ctx, env);
  }

  async fetch(request: Request): Promise<Response> {
    if (request.method !== "POST") {
      return new Response("Method not allowed", { status: 405 });
    }
    try {

      const requestData = await request.json();
      const { url, body }: any = requestData;
    
      if (!url) {
        return new Response("Missing URL in request body", { status: 400 });
      }

      const response = await fetch(url, {
          method: "POST",
          headers: {
            "Content-Type": "application/json",
          },
          body: JSON.stringify(body)
        });
      if (response.ok) {
        return new Response(JSON.stringify(response.json()), {
          headers: { "Content-Type": "application/json" },
        });
      } else {
        return new Response(`CreatorDO Error: ${ await response.text()}`, {
          status: 500,
        });
      }
    } catch (error: any) {
      return new Response(`CreatorDO Error: ${error.message}`, {
        status: 500,
      });
    }
  }
}