US President Donald Trump has announced in his State of the Union speech that he will hold a second nuclear summit with North Korea's leader this month, the BBC reports.

In an address to the nation with the theme "Choosing Greatness", he vowed once again to build a border wall.

While appealing for political unity, the Republican president also said "ridiculous partisan investigations" could damage US prosperity.

In a rebuttal, Democrats accused Trump of abandoning US values.

His primetime address came less than a fortnight after he backed down to end the longest ever US government shutdown when Democrats refused to fund a US-Mexico border wall.

Federal agencies could close again if no spending plan is agreed by the end of next week.

The president said in his 82-minute speech on Tuesday, February 5 night that he would meet Kim Jong-un in Vietnam from 27-28 February.

"Much work remains to be done," Mr Trump said, "but my relationship with Kim Jong-un is a good one."

Trump and Kim's meeting last June in Singapore was the first ever between a sitting US president and a North Korean leader.

While Pyongyang has not conducted any atomic or ballistic missile tests since last summer, it has yet to agree to dismantle its nuclear weapons programme.