Based on field observations and some discussions with U.S.
( Based ( on ( ( ( field observations ) and ) ( ( some discussions ) ( with U.S. ) ) ) ) )
(ROOT (PP (VBN Based) (PP (IN on) (NP (NP (NN field) (NNS observations)) (CC and) (NP (NP (DT some) (NNS discussions)) (PP (IN with) (NP (NNP U.S.))))))))
It was based on field observations and discussions with the us. 
( It ( ( was ( ( based ( on ( field ( ( observations and ) discussions ) ) ) ) ( with ( the us ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBD was) (VP (VBN based) (PP (IN on) (NP (NN field) (NNS observations) (CC and) (NNS discussions))) (PP (IN with) (NP (DT the) (PRP us))))) (. .)))