U.S. stock index futures were slightly higher Monday morning.

At around 2:00 a.m. ET, Dow futures climbed 23 points, indicating a slightly higher open of just 2 points. The S&P 500 and Nasdaq indexes were also marginally higher.

U.S. equities have enjoyed a strong rally in December, with the main indexes hitting record highs last week amid year-end optimism in markets. Monday marks day four of the so-called Santa Claus rally period, which is typically seen as giving a boost to stocks.

Market sentiment has been boosted by improving mood music over U.S.-China trade relations. The world’s two largest economies agreed earlier this month to a so-called “phase one” trade deal.

But political concerns continue to simmer in the background, after President Donald Trump was impeached by the House of Representatives. The president over the weekend retweeted a post that included the alleged name of the whistleblower whose complaint led to Trump’s impeachment.

In terms of data, U.S. international trade and retail inventories figures for November are due to be released at 8:30 a.m. ET.