Former US vice president and anti-global warming campaigner Al Gore and his wife Tipper have told friends that they will separate after four decades of marriage, an aide said Tuesday.

"They've asked for privacy during this time, for them and their family," said Kalee Kreider, of the Office of Al and Tipper Gore.

Kreider confirmed that the Gores -- whose affection for each other was evident at social gatherings in Washington for 40 years, notably during his failed 2000 White House run -- had let friends know of their plans by email.

"We are announcing today that after a great deal of thought and discussion, we have decided to separate," they said in the message, first reported by the online publication Politico.

"This is very much a mutual and mutually supportive decision that we have made together following a process of long and careful consideration. We ask for respect for our privacy and that of our family, and we do not intend to comment further," they said.

Al Gore, 62, won the Nobel peace prize in 2007 for his work on raising awareness of climate change, and an Oscar that same year for his documentary "An Inconvenient Truth" sounding the alarm over global warming.

Mary Elizabeth "Tipper" Gore, 61, is a photographer who chronicled her life as the vice president's spouse as well as Al Gore's 2000 presidential campaign and has won praise for her work as an advocate for mental health issues.

The two met at his senior prom dance in 1965, married in May 1970, and have four children.

At the August 2000 Democratic presidential convention, the two had made headlines by sharing a long kiss on the stage after she introduced him and he prepared to accept the party's nomination.

The embrace, though derided by some as choreographed, helped bring home Gore's message that he was "my own man" at a time when then-president Bill Clinton's tawdry affair with former White House intern Monica Lewinsky loomed over the campaign.

Al Gore was Clinton's vice president from January 1993 to January 2001, and fought a bitter battle over disputed November 2000 election results in Florida before conceding to George W. Bush, who served two terms and left office in January 2009.

The former vice president left the political limelight and said he was no longer interested in holding elected office, instead pursuing a range of projects including his worldwide climate change work.

Tipper Gore is also known for co-founding the Parents Music Resource Center to combat offensive lyrics in pop music, a campaign that resulted in record labels attaching "Parental Advisory" stickers to music with adult language.

The effort drew widespread criticism from musicians and civil liberties activists, who decried what they saw as censorship.