President Donald Trump criticized his former national security advisor and said the U.S. government should spend less time worrying about Russian President Vladimir Putin.

Donald Trump has erupted at Europe, claiming "we should spend less time worrying about Putin" in a fiery post on social media. The outburst is the latest in an exploding row between the US president and Ukraine.

Concerns about US foreign policy and national security are in the limelight amidst Donald Trump's growing ties with Russia. This comes after Ukrainian President Zelensky left the White House early after a contentious meeting on Friday.

Tempers flare between Ukraine's President Zelensky and US President Donald Trump during a meeting in the White House.

A top adviser to President Donald Trump said on Sunday that the United States needs a Ukrainian leader who is willing to secure a lasting peace with Russia but that it is not clear Ukrainian President Volodymyr Zelenskiy is prepared to do so.