CBC News will carry his anticipated resignation live from Parliament Hill starting at 10 a.m. ET.
Baird is leaving politics, and his resignation is expected to take effect immediately, leading to speculation he has a new job lined up. His experience and profile are expected make him attractive to the private sector. Sources close to Baird say that after 20 years in public office, it was simply time to seek other opportunities.
Baird's expected departure from cabinet, along with the resignation of Jim Flaherty a month before his death last year, mean two of Harper's most powerful ministers will have left the prime minister's inner circle in less than a year.
As foreign affairs minister, Baird has overseen a busy file, handling Canada's diplomatic response to the war in Libya, the crisis in Ukraine, the Palestinian push for statehood, the coalition mission in Iraq and, most recently, the case of jailed Canadian-Egyptian journalist Mohamed Fahmy. He also took a hard line against the abuse of gays and lesbians around the world, and focused the Canadian government's attention on the issue of forced marriage.
Baird represents the riding of Ottawa West-Nepean and was nominated last March as the Conservative candidate in the newly created riding of Nepean for the next federal election, which must be held by Oct. 19 at the latest.
Baird, 45, has been in politics most of his adult life. He was first elected as an MP in 2006 after a decade in provincial politics in Ontario, where he served in former premier Mike Harris's cabinet.
A source close to Baird said he still supports the prime minister and will campaign for the party in the election.
Will get pension earlier
By not running in 2015, Baird will also qualify for his pension, under an old rule, at age 55. Parliament increased the qualifying age to 65 years old but that policy only covers those who are elected or re-elected in 2015.- PHOTOS: John Baird's Harper cabinet years
After CBC News surprised many with early word of his departure Monday night, Twitter had both darts and laurels for the veteran Conservative as his news spread.
The CBC's Matthew Kupfer reported "surprise and shock" early Tuesday morning from the streets in Baird's west Ottawa riding. Constituents said that as both a provincial and federal representative Baird was proactive for his community and he'd be missed.
One told CBC that if Baird is leaving to take on a prominent international role, it would be "good for Canada's reputation."
In naming International Trade Minister Ed Fast interim foreign affairs minister, Stephen Harper's office reaches for their 2008 playbook: when former foreign affairs minister Maxime Bernier was forced to resign amid controversy, then Trade Minister David Emerson was assigned to cover the entire foreign affairs and international trade department on an interim basis. (Emerson's new responsibilities were confirmed in a cabinet shuffle a month later.)