Trump-Putin summit overshadowed by Mueller investigation

US President Donald Trump is preparing for his controversial summit with Russian leader Vladimir Putin but investigators in the US are continuing to look into their relationship in the run up to the election.  

On Friday, the US Justice Department charged 12 Russian intelligence officers with interfering in the 2016 US presidential election. 

TRT World's North American correspondent Jon Brain reports from Washington.

For more than a year now, Special Counsel Robert Mueller has cast a shadow over the American presidency with his dogged investigation of claims that Trump's election campaign team colluded with the Kremlin.

If Trump is found to have broken the law he could face not just impeachment but a criminal prosecution.

"This is so unprecedented. We've never seen something like this and if this gets uncovered as much as we think it's going to this could be the biggest scandal of American democracy in recent times", said Mueller who was appointed special counsel last May to investigate election meddling by Russia.

The following month the inquiry was expanded to include allegations of obstruction of justice by the President.

In October 2017 several former Trump campaign managers were charged with conspiracy against the US.

And within the past few days 12 Russian intelligence officers have been charged with hacking US voting lists.

"Acres of newsprint and hours of television airtime have been devoted to the Mueller investigation. Virtually every person of significance in the US seems to have given their opinion on it. 

Except for one. Mueller himself hasn't given a single interview outlining the progress of his inquiry. We don't know what he's found or even exactly what he's looking for", said Brain.

But Trump has made it clear he will follow the evidence wherever it leads him. 

Some of Trump's opponents believe it might lead all way to the Oval Office.