1. Trump-Kim summit: Markets were calm after President Donald Trump and Kim Jong Un concluded their historic summit in Singapore.

US stock futures were steady.

European markets posted small gains in early trading. Most Asian markets closed higher, while South Korea's KOSPI index dipped by 0.1%.

Nearly five hours of unprecedented and surreal talks between Trump and Kim culminated with declarations of a new friendship but just vague pledges of nuclear disarmament.

On Monday, the Dow Jones industrial average, S&P 500 and Nasdaq closed with small gains.

2. AT&T decision time: A US federal judge is expected to rule on the fate of AT&T's (T) $85 billion bid to acquire Time Warner (TWX) at 4:00 p.m. ET.

The Justice Department sued to block the deal. It argues that the combination would give AT&T (T) the power to charge its competitors more for Time Warner's content, or to block the content entirely from the likes of Comcast (CCZ) and Verizon (VZ).

Time Warner owns HBO, Warner Bros. and the Turner networks, including CNN.

AT&T and Time Warner say they need to join forces to compete with new competitors such as Netflix (NFLX) and Amazon (AMZN). AT&T has argued that prices would not necessarily go up, and that it would have no reason to keep its content from competitors.

If the deal is approved, reports have been swirling that Comcast (CMCSA) could then formally make a takeover offer for 21st Century Fox (FOX).

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3. Brexit votes: Traders will be closely monitoring the British pound as UK lawmakers vote on the government's Brexit plans.

The pound could "be a Brexit punchbag ahead of a potential 48 hours of Commons debate and voting on the Brexit Withdrawal Bill," warned analysts at Accendo Markets.

The United Kingdom is scheduled to exit the European Union at the end of March 2019. Time is running out to sort out all the legalities and details, and businesses are clamoring for clarity.

The pound is currently trading around $1.34, up slightly overnight.

4. Earnings and economics: Casey's General (CASY) and Lands' End (LE) will release earnings before the open. H&R Block (HRB) will follow after the close.

The US Bureau of Labor Statistics will release its May inflation report at 8:30 a.m.

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5. Coming this week:

Tuesday — H&R Block (HRB) earnings; AT&T-Time Warner decision
Wednesday — Federal Reserve interest rate decision
Thursday — US retail sales for May
Friday — Deadline for the White House to publish Chinese tariff list covering $50 billion worth of products