Wall Street futures slipped Monday after talks between the U.S. and Iran over the weekend failed to deliver a deal to end the war.

The declines indicate that any relief from the ceasefire reached last week could be fleeting, underscoring the risks of leaning too heavily into bullish bets when the geopolitical environment remains uncertain.

The main U.S. stock indexes logged their second consecutive week of gains on Friday on hopes that the peace talks in Pakistan would bear fruit.

On Monday, however, Dow E-minis fell 306 points, or 0.64%, as of 7:36 a.m. EST, S&P 500 E-minis dropped 39.50 points, or 0.58%, and Nasdaq 100 E-minis slipped 140.50 points, or 0.56%.

Adding to the unease, the U.S. military is hours away from beginning a blockade of all maritime traffic entering or leaving Iranian ports and coastal areas, in a move aimed at ramping up pressure on Tehran.

"For the Iranians who up to now have felt that time is on their side, it puts pressure on their allies to encourage Iran to come to the table to make a deal," said William Blair's macro analyst Richard de Chazal.

The CBOE Market Volatility Index, the market's fear gauge, climbed to 21.32 points.

The shift in sentiment was also visible across other asset classes, with investors gravitating toward the safe-haven U.S. dollar while trimming exposure to equities across geographies.

Oil prices jumped back above $100 a barrel, aggravating inflation worries after data last week showed that a record surge in the cost of gasoline and diesel prompted the biggest increase in U.S. consumer prices in nearly four years in March.

"We are back in the realm of a wide range of plausible outcomes, from another round of negotiations during a patchy ceasefire... to a full resumption of hostilities," said Hasnain Malik, Tellimer's geopolitical risk and EM equity strategist.

Investor attention now turns to the start of the U.S. earnings season, with Goldman Sachs scheduled to report before the bell. Commentary from the investment banking giant's executives will be parsed for clues on how the Middle East conflict, now in its seventh week, is impacting the economy and capital markets.

Goldman shares inched 0.3% higher in premarket trading, outperforming most of its Wall Street peers.

Travel-related stocks fell, with carriers such as Delta Air Lines and JetBlue Airways down 1.8% and 1.9%, respectively, on concerns that higher oil prices might push up fuel costs.

Energy stocks gained, with Chevron, Exxon Mobil and ConocoPhillips climbing 2.2%, 2.5% and 2.8%, respectively.

Sandisk added 1.4% premarket as the memory chipmaker was on track to join the Nasdaq-100 index on April 20.