NEW YORK (Bloomberg) — Evan Greenberg, the chief executive officer of Chubb Ltd, mocked “wannabes” at smaller insurers who are seeking to expand by guarding commercial clients against trade disruption or political instability in international markets.

“They’re scratching for business, they don’t want to shrink,” Greenberg said of rivals in a conference call, without naming individual companies. “They think growth and just the top line equal strength.”

Greenberg formed one of the world’s largest insurers by combining his Ace Ltd this year with Chubb Corp. He joins Warren Buffett, the CEO of Berkshire Hathaway, in warning that upstarts eager for business may be taking on unsustainable risks. Both executives have been willing to lose market share rather than sell insurance for what they consider to be too low a price.

Coverage for trade credit and political risk can be particularly dangerous, given that the global economy faces growing protectionism “and geopolitical risk everywhere”, Greenberg said. The policies can protect against confiscation of property and include so-called contract-frustration insurance.

“Sounds like a brilliant time to get into that business,” he said sarcastically of rivals. “I wish them a lot of luck because that’s all they got going for them.”

Second-quarter policy sales were $7.64 billion, or 5.8 per cent less than the combined figure for Ace and the old Chubb in the year-earlier period, the Zurich-based company said in a statement after markets closed on Tuesday, citing competitive market conditions and currency fluctuations.

Greenberg also warned that protectionism will limit economic growth. UK voters supported a plan last month to exit the European Union. In the US, Republican presidential nominee Donald Trump and Democrat Hillary Clinton have criticised the Trans-Pacific Partnership, the trade deal favoured by her political ally, President Barack Obama.

The characterisation that global commerce has “been evil and has damaged our country and has damaged the world is just so misguided”, Greenberg said. Also, the idea that immigration “is somehow our enemy is again misguided populism and feeding on the suffering of those who may vote”, he said.

Trump has vowed to build a wall along the US border with Mexico, a plan opposed by Clinton.