c# Can a "task method" also be an "async" method?

I'm trying to get the hand of the new async CTP stuff and I'm probably confusing myself here.. I can have this "task method", with no problem:

    public static Task<String> LongTaskAAsync() {
        return Task.Run(() => {
            return("AAA");
            });
        }

But what if I need the task to execute another task, can I mark it as "async" and use "await"? I tried this:

public async static Task<String> LongTaskAAsync() {
        await Task.Delay(2000);
        return Task.Run(() => {
            return("AAA");
            });
        }

But then mysteriously get this compiler error: Since this is an async method, the return expression must be of type 'string' rather than Task<string>

What am I missing here?