On the large company list OMXS30, the decline was broad. Only 4 out of 30 shares went up, among them the telecom giant Ericsson which rose marginally 0.2 percent.
The worst performers were the defense group Saab and the clothing giant H&M, down 3.8 and 2.4 percent respectively.
Leading stock exchanges in Europe also declined after a weak start upwards. The DAX index in Frankfurt lost the most, falling around 1 percent.
The agreement between the EU and the US means import duties of 15 percent on goods from the EU, including cars. The union commits itself at the same time to invest in and buy energy from the US for several thousand billion kronor.
The agreement seemed to appeal to American investors, and the indexes on Wall Street rose in the initial trading, but also there many prices fell back later. The electric car manufacturer Tesla took the lead with an increase of 3.7 percent after a few hours of trading.
With Monday's decline included, the Stockholm stock exchange's OMXS index has now risen 2.8 percent since the turn of the year.
