By Alexandra Gibbs, CNBC–

U.S. stock index futures tumbled deep into the red ahead of Monday’s open, following negative trade seen in markets overseas.

Around 5:40 a.m. ET, Dow futures fell 161 points, indicating a negative open of 138.89 points. The Nasdaq and the S&P 500 futures indicated a downbeat start to their respective trading session.

As another trading week kicks off, market-watchers are likely to be digesting any new information surrounding global trade tensions, amid fresh economic data.

Last week, President Donald Trump took to Twitter to threaten another set of tariffs, this time on the European Union. On Friday, the U.S. incumbent warned of a 20 percent tariff on all car imports from the EU, stating that if the bloc refused to remove duties on U.S. cars, then Washington would have no choice but to act on these levies.

Consequently, European markets were under pressure Monday.

Trump added over the weekend that “all countries that have placed artificial trade barriers and tariffs on goods going into their country” should get rid of them, or face reciprocation from the U.S.

Coming up Monday, at 10 a.m. ET, new home sales data is scheduled to be published, followed by the Dallas Fed’s Texas manufacturing outlook survey at 10:30 a.m. ET.

Oil prices pointed in different directions, as traders digested the latest output agreement secured by members of OPEC, which looks to raise output, in light of disruptions in the market.

CarnivalCCL is expected to publish its latest corporate earnings.