Posting using REST API fails on Swift TwitterKit

let client=TWTRAPICclient()
    varclientError: NSError?
    letendPoint="https://api.twitter.com/1.1/statuses/update.json"

    let params=["status": "testTweet" ]

    let request = client.URLRequestWithMethod("POST", URL:endPoint, parameters:params, error:&clientError)

    client.sendTwitterRequest(request){(response,data,connectionError)->Void in
        if(connectionError==nil){
            print("success");
        }
        else{
            print("Error:\(connectionError)")
        }
    }

 Optional (Error Domain=TwitterAPIErrorDomain Code=220 
"Request failed: forbidden (403)" 

UserInfo={NSLocalizedFailureReason=Twitter API error:
 Your credentials do not allow access to this resource. (code 220), 
 NSErrorFailingURLKey=https://api.twitter.com/1.1/statuses/update.json,
 NSLocalizedDescription=Request failed: forbidden (403)}