This week’s G-20 meeting in Germany offers the U.S. president an opportunity to meet with world leaders on a one-to-one basis, which will help his credibility, according to John Studzinski, vice-chairman of investment firm The BlackStone Group.

President Donald Trump will arrive in Poland later today, before heading to Hamburg in Germany for the G-20 leaders summit on Friday and Saturday. It’ll be the first time he’s met several of the leaders, including Russian President Vladimir Putin.

“The president has his style and it’s a style his constituents continue to support. It’s a style that world leaders are not accustomed to,” Studzinski told CNBC’s Squawk Box on Wednesday.

“The Chinese are not entirely that comfortable with it, because the Chinese like to understand a leader and understand how they’re going to think about things.”

There have been several complaints about Trump’s approach as a leader, including his use of the social media platform Twitter to attack and criticize opponents.

“Certainly in the short term you’ve got a lot of comments from Congress about (his behavior) eroding the credibility of the president,” he said.

“I would say, at the end of the day this is his second big meeting coming up in Hamburg in a few days and it’s another chance for him to develop some much more powerful one-on-one interactions.”

Donald Trump is a personality-driven leader, which is why people want to meet with him one-on-one, according to Studzinski.

“Where he has one-on-one interactions, the way he’s had with many countries, like Japan for example, it does make a big difference,” he said.

Studzinski also talked about the president’s impact on the financial markets. U.S. stock markets have seen record highs since the election in November, as they hoped the Trump administration would deliver key reforms to the market.

The Dow Jones and Nasdaq are both up more than 20 percent since the election.

“Markets don’t lie and the market is still very positive about Donald Trump and the U.S., but there’s probably a view that if there isn’t any major changes in health care legislation, trade or taxes in the next three months, then you could see (an) adjustment,” Studzinski said.

“Whether it’s 8 percent, 5 percent, 10 percent, there’s certainly more downside than upside.”

William Vereker, global co-head of corporate client solutions at UBS, was more critical.

“The scope for Trump to disappoint gets greater every week and the expectation of tax change reform, infrastructure investment, has been so great that if it’s not delivered over the next 6 to 9 months that will have an effect on the markets,” he said on CNBC’s Squawk Box.

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