The official did not provide a timing for the signing of the order, first reported by the Wall Street Journal.
The United States has never had an official language at the federal level but some US states designate it as their official language.
The Republican president has made opposition to illegal immigration a hallmark of his White House runs and has embraced using English in public life.
During his first presidential campaign, Trump chided Republican rival Jeb Bush for speaking another language on the campaign trail.
He told a news conference in New York in 2015 that "We're a nation that speaks English".
Trump's executive order would rescind Democratic President Bill Clinton's federal requirement that agencies and other recipients of federal funds provide language assistance to non-English speakers, the Wall Street Journal said.
Among the executive orders Trump has signed since taking office January 20 is one aimed at preventing taxpayer dollars from supporting illegal immigration, barring the use of federal money for migrants in the country illegally.
There are 32 US states that have adopted English as their official language, according to ProEnglish, a group advocating English as an official language.
The issue has been problematic for certain states including Texas, where the use of Spanish in public life has sparked controversy over the years.
A Texas state senator in 2011 demanded that an immigrant rights activist speak English not his native Spanish at a legislative hearing.
That rekindled a decades-old debate over whether it is proper to speak Spanish in Texas, which was once a part of Mexico and, before that, a part of the Spanish Empire.
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