President Donald Trump embarks on his first foreign trip this week. First stop: Saudi Arabia. Second stop: Israel. Then it's on to the Vatican to meet the Pope, the NATO Summit in Brussels and G7 in Italy. The trip is intended to bolster Trump's standing on the world stage, but his divulging previously classified information obtained by Israel to adversary Russia and the questions swirling about former FBI Director James Comey and former National Security Advisor Michael Flynn may create setbacks on that front. Two former U.S. ambassadors spoke with CNBC about Trump's standing among foreign leaders and what he needs to do to win credibility. Here are parts of the conversations:

Daniel Shapiro, former U.S. ambassador to Israel, delivers a speech in Herzliya, Tel Aviv, on March 13, 2013. Jack Guez | AFP | Getty Images

Daniel Shapiro, former U.S. ambassador to Israel under President Barack Obama (2011-2017) and current senior fellow at the Institute for National Security Studies in Tel Aviv CNBC: President Trump is going to be meeting with Prime Minister Benjamin Netanyahu this week. How do you think the Israelis are discussing this ? Shapiro: I expect, in private, the PM will have to have some very frank conversations with the president to explain to him the damage that's been done. And to confirm that there will be procedures put in place and that the president's own personal discipline will be such that this won't be repeated. CNBC: What does Trump need to do to shore up his credibility ahead of this trip?



Shapiro: I think he needs to show more discipline. I think he needs to spend time with his experts and really master the details and the briefings that he receives...and read through all that material. Foreign policy and national security is not something you can just wing. I think he's going to have to demonstrate a different kind of rigor and discipline than he has shown so far to win the confidence of many of the foreign leaders he deals with. CNBC: Do you think he's capable of that kind of discipline? Shapiro: I'm not sure. You know, he's 70 years old. He's obviously conducting his affairs in government in a similar way that he has conducted his business affairs throughout his adult life. It's difficult for a person to change at that stage of life but I think it's imperative for our country, for his success that he try and do so. CNBC: What are your colleagues and contacts in Israel saying about all of this? Shapiro: People are trying to be polite. Everybody cares about this relationship. Everybody wants to see the United States succeed and the U.S.-Israel relationship continue to be as strong as it's been over the last number of years. But there is a recognition that we're dealing with something unusual and maybe unprecedented in American history — a president who is as unpredictable and inexperienced as this one and potentially compromised in serious ways. And that has Israelis — who depend so much on the United States for their own security — very nervous.

Frank Lavin, then U.S. ambassador to Singapore, toasts with Singapore's Ambassador-at-large Tommy Koh at the U.S. embassy in Singapore on August 1, 2003. Roslan Rahman | AFP | Getty Images