NEW YORK -- Top American CEOs took a dimmer view of the country's economy for the sixth consecutive quarter amid the continuing U.S.-China trade tensions and slowing global growth, a new survey shows.

The Business Roundtable CEO Economic Outlook Index, updated Wednesday, sank more than 10 points to 79.2 for the third quarter, the lowest since President Donald Trump took office. The rating, which peaked at 118.6 in the first quarter of 2018, has fallen below the index's historical average of 82.7.

The index is derived by polling members of the Business Roundtable, an association of chief executives from U.S. companies. The group made headlines last month when it pivoted from a shareholder-first maxim to champion a stakeholder-based redefinition of corporate purpose.

"This quarter's survey shows American businesses now have their foot poised above the brake, and they're tapping the brake periodically," Joshua Bolten, president and CEO of the Business Roundtable, said in a statement. "Uncertainty is preventing the full potential of the economy from being unleashed, limiting growth and investment here in the U.S."

One in five CEOs who participated in the survey said they expect declining sales at their company in the next six months, compared with just 9% last quarter. And 20% also expect layoffs over that time. The executives project U.S. gross domestic product to rise 2.3% for 2019, down from their 2.6% estimate last quarter.

The Business Roundtable cited "U.S. trade policy and foreign retaliation" as well as "slowing global economic growth" as the likely causes of the deteriorating business confidence.

JPMorgan Chase CEO Jamie Dimon, who chairs the Business Roundtable, said plans for hiring and capital investment remain healthy among members, but that "uncertainty about U.S. trade policy" is among the concerns dampening business sentiment.

The survey came after Trump escalated the trade war with Beijing in early August by announcing 10% tariffs on $300 billion of Chinese imports, a move that sparked tit-for-tat actions from both sides. The U.S. president had previously hinted at a 25% tariff hike on those goods, but the proposal drew staunch opposition from American businesses large and small.

After the poll closed, China and the U.S. both made gestures toward reconciliation last week with tariff exemptions and delays, a development welcomed by the stock market. A new round of trade negotiations is set for next month in Washington.