• The House intends to vote on the debt ceiling deal Wednesday.
• JPMorgan CEO Jamie Dimon called on China and the U.S. to iron out their differences.
• A.I. could pose a threat as serious as nuclear war, top scientists and executives warn.

Here are the most important news items that investors need to start their trading day:

1. Mixed-up May

The major U.S. stock indices are in a mixed state as May ends. The tech-heavy Nasdaq, on one hand, is up more than 6% heading into the final session of the month, driven in large part by the explosion of artificial intelligence. The Dow, on the other, is down more than 3%. And the broad S&P 500 has risen only slightly in May. The end of the month also brings the U.S. closer to a potential debt default, if Congress doesn't act (more on that below). Follow live market updates.

2. Huge vote coming up

The debt ceiling bill, forged as a compromise between President Joe Biden and House Speaker Kevin McCarthy, is headed for a vote Wednesday night on the floor of the House. The measure cleared a key hurdle Tuesday evening, making it out of the House Rules Committee with a 7-6 vote. McCarthy is facing loud resistance from a group of ultra conservatives in his own party, meaning he'll have to depend a great deal on Democrats to get the bill to the Senate. There, Democrats have their own slight majority. Time is running short, too. The Treasury Department has warned it could run out of money Monday, just five days away.

3. Dimon goes to China

JPMorgan Chase CEO Jamie Dimon, speaking in Shanghai, called on the U.S. and Chinese governments to cool it and find a way to better work together. "You're not going to fix these things if you are just sitting across the Pacific yelling at each other, so I'm hoping we have real engagement," Dimon said, referring to trade and security issues, as he spoke at the JPMorgan Global China Summit. The banker isn't the only major U.S. CEO who visited China this week against the backdrop of intensifying tension between the countries. Tesla boss Elon Musk met several top officials and executives during his trip.

4. One sentence to warn the world

Warnings about artificial intelligence are coming almost as rapidly as advancements in the technology. The most recent one, coming in at just one sentence long, might be the starkest yet, however. "Mitigating the risk of extinction from AI should be a global priority alongside other societal-scale risks such as pandemics and nuclear war," reads an open letter posted by the Center for AI Safety. It's signed by a slew of top scientists and executives, including Sam Altman, the head of ChatGPT creator OpenAI. Even as ChatGPT explodes in popularity, reaching more than 100 million users and prompting several competitors to join the race, Altman has been one of the voices calling for regulation to keep AI from becoming something more than a mere tool for humanity. And that seems pretty serious.

5. Mortgage demand slumps

Mortgage demand is at its lowest point in three months, according to the Mortgage Bankers Association. Rates shot up again recently, nearly hitting 7% by some measures, as it became clear that the Federal Reserve wasn't going to cut its benchmark rate any time soon. The supply of homes remains tight, as well, and prices look like they're going higher again. "While refinance demand is almost entirely driven by the level of rates, purchase volume continues to be constrained by the lack of homes on the market," Michael Fratantoni, the Mortgage Bankers Association's chief economist, said in a release.

– CNBC's Jesse Pound, Christina Wilkie, Emma Kinery, Elliot Smith, Sheila Chiang and Diana Olick contributed to this report.

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