(S (S (NP (BASENP (NNP Prime) (NNP Minister) (NNP Blair)) (CC and) (BASENP (NNP Chancellor) (NNP Brown))) (VP (VBP are) (VP (VBN agreed) (PP (IN on) (NP (BASENP (DT the) (NN need)) (SBAR (S (VP (TO to) (VP (VB retain) (BASENP (DT a) (JJ nuclear) (NN deterrent))))))))))) (PERIOD .))