(S (S (S (BASENP (DT The) (JJ unmarked) (NN border)) (VP (VBZ remains) (VP (VBN disputed)))) (CONJP (COMMA ,) (CC and)) (S (BASENP (DT the) (NNS nations)) (VP (VBP have) (VP (VP (VP (VP (VBN built) (PRT (RP up))) (BASENP (NNS troops))) (PP (IN on) (NP (BASENP (DT each) (NN side)) (PP (IN of) (BASENP (DT the) (NN border)))))) (COMMA ,) (S (VP (VBG keeping) (S (BASENP (DT the) (NN situation)) (ADJP (JJ tense))))))))) (PERIOD .))