Secret Nixon tapes reveal intimate chat with Brezhnev - including smoking tips

Secretly recorded tapes from a system installed by Richard Nixon have revealed the then US president and his Soviet counterpart Richard Nixon chatting warmly before a historic summit in 1973.

The long talk was captured on a hidden recording system that Nixon used to tape 3,700 hours of conversations between February 1971 and July 1973.

The final installment of those tapes - some 340 hours worth - have been released by the US National Archives and Records Administration, along with more than 140,000 pages of text documents. However, hundreds of hours remain sealed for national security and privacy reasons.

On 18 June 1973, the two leaders met with only an interpreter present and discussed personal topics, including their family lives. The conversation happened before a historic seven day summit began, part of Nixon's strategy to ease tensions with the Soviet Union.

Part of the light hearted conversation sees the two men joking about how the jetlagged Brezhnev would get through the official dinner - and how the Soviet leader cut down on his smoking habit.

"You see, I have a cigarette box there. It has a special timing mechanism and I can’t - I won’t be able to open it for an hour," Brezhnev tells Nixon.

"Oh, how's it open?" asks the US president.

"See, the mechanism, the timing mechanism is now working and I won’t be able to open that for another hour. In one hour it will unlock itself," Brezhnev replies.

"That's a way to discipline yourself," laughs Nixon.

Later, the conversation takes a more serious turn.

"We must recognize, the two of us, that ... we head the two most powerful nations and, while we will naturally in negotiations have some differences, it is essential that those two nations, where possible, work together," Nixon told Brezhnev.

"If we decide to work together, we can change the world. That's what - that's my attitude as we enter these talks."

The newly released recordings also show that in the hours after delivered the then president delivered the first major national address about the Watergate scandal that would eventually drive him from office, two future presidents called him to express their private support: Ronald Reagan and George HW Bush.

Nixon is still the only US president to resign from office, which he did as a result of the Watergate scandal, when burglars tied to his re-election committee broke into the Democratic headquarters to get dirt on his political adversaries.

Reagan, governor of California at the time, called late in the evening of 30 April, 1973, to support Nixon.

"I just want you to know, we watched and my heart was with you. I know what this must have been and what this must have been in all these days and what you've been through," Reagan said.

"You can count on us, we're still behind you out here and I wanted you to know that you're in our prayers."

The recordings cover 9 April, 1973, to 12 July, 1973, the day before the existence of the covert recording system was revealed to a US Senate committee investigating Watergate.

Previous tape releases show the president as a paranoid man who was not afraid to use bare-knuckle tactics to crush the enemies he saw all around him.

Earlier tapes show Nixon's obsession with the Kennedy family. He considered the late senator Ted Kennedy to be a huge political threat and had him spied on to try to catch him in a compromising position.