addis ababa unite state consider pressure south sudan president salva kiir peace withdraw aid may work u.s. envoy unite nations nikki haley say ahead visit south sudanese refugees ethiopia tuesday haley plan visit gambella western ethiopia nearly 350,000 refugees flood across border south sudan since country spiral civil war 2013 two years gain independence sudan really think hard pull u.s. aid president kiir care haley say care people suffer concern know make difference conversation try see exactly move president kiir ... start really look create safe position people tell reporters addis ababa late monday haley week senior member u.s. president donald trump administration visit south sudan due meet kiir first see conflict threaten spillover deadly cross-border raid gambella ethiopia gunmen south sudan trump new aid administrator mark green visit south sudan last month tell kiir washington review policy toward government call kiir end violence implement real ceasefire war south sudan spark feud kiir former deputy riek machar plunge part world young nation famine force third population million people flee home machar flee hold south africa stop stir trouble source tell reuters december fragile peace deal break last year amid gun battle soldier rebel capital juba international efforts bring war side new talk succeed see deaths see anymore famine get start see situation start get good think pressure go continue president kiir make difference haley say trump administration last month impose sanction two senior south sudanese officials former army chief role conflict atrocities civilians attack international missions south sudan u.s. mull south sudan pressure cut aid may work u.n. envoy