U.S. stock futures declined again on Monday as Saudi Arabia faced growing pressure over a missing critic of the kingdom.

Future contracts on the S&P 500 index, Dow Jones Industrial Average and Nasdaq were all in the red, indicating that investors remain cautious about U.S. stocks after last week’s sharp sell-off. Europe's STOXX 600 dropped to a new 22-month low as Brexit talks were put on hold, and the oil market was also in focus with Brent crude rising 1% to $81.28 per barrel.

President Donald Trump’s feud with Saudi Arabia over a missing journalist poses one of the biggest risks to stock market sentiment at the beginning of the week. In an interview aired Sunday on “60 Minutes,” President Trump threatened “severe punishment” if an investigation finds the kingdom responsible for the disappearance of dissident Saudi journalist Jamal Khashoggi. Turkish officials have said the U.S. resident was murdered inside the Saudi consulate in Istanbul.

The kingdom, which said it “plays an effective and vital role in the world economy,” warned that it would retaliate if any action is taken against it. "If the price of oil reaching $80 angered President Trump, no one should rule out the price jumping to $100, or $200, or even double that figure," wrote Turki Aldakhil, general manager of the Saudi-owned Al-Arabiya news channel, in an op-ed.

“Another geopolitical hot spot for the U.S. administration to navigate but this one extremely testy given that President Trump has been pressuring Saudi to up supply to counter the U.S.-led Iran oil sanction,” Stephen Innes, head of trading in the Asia Pacific for OANDA, wrote in a note, according to MarketWatch.

The U.S. government’s tough stance against Saudi Arabia comes after several high profile figures decided to boycott a major investment conference in the kingdom. Ford Motor Co. (F) Chair Bill Ford and JPMorgan Chase & Co. (JPM) CEO Jamie Dimon are the latest to drop out of the event. Others like Uber chief Dara Khosrowshahi, World Bank president Jim Yong Kim and British entrepreneur Richard Branson have also recently distanced themselves from Saudi Arabia over the disappearance of Khashoggi.

IMF Trade War Warning

During the interview with CBS News, the president also warned that he could impose further tariffs on China. His threats came as the International Monetary Fund (IMF) provided a grim assessment of the global economy during an annual meeting in Bali, Indonesia.

Economists warned that the world economy is plateauing and risks becoming weaker if trade tensions are not resolved. During the meeting, the IMF estimated a full-blown trade war would shave more than 0.8 percent off global output in 2020, reported Bloomberg.