HAMBURG (REUTERS) - Even US First Lady Melania Trump was powerless to keep Friday's (July 7) first face-to-face meeting of the US and Russian presidents from running nearly twice as long as planned.

US Secretary of State Rex Tillerson said he tried several times to remind US President Donald Trump about the ticking clock during his meeting with Russian President Vladimir Putin.

"One of the reasons it took a long time... is because once they met and got acquainted with one another fairly quickly, there was so much to talk about.

"There was just such a level of engagement and exchange that neither of them wanted to stop," Tillerson told reporters.

He said the two men connected quickly and had "a very clear positive chemistry."

Trump and Putin met for two hours and 15 minutes - much longer than planned.

"Several times I had to remind the President. People were sticking their heads in the door. They even... sent the First Lady at one point to see if they could get us out of there. But it didn't work," Tillerson said.

"We went another hour after she came in to see us. Clearly she failed," he added.