Dec 17 (Reuters) - Manulife Financial Corp (MFC.TO), Canada"s biggest life insurer, on Friday became the latest financial company to delay its return-to-office plans for its North American staff amid rising COVID cases and the fast-spreading Omicron variant, according to a memo seen by Reuters. Manulife had earlier announced that staff in its North American offices would be returning to offices on Jan. 24. "We"ve all been hearing a lot in the news about the Omicron variant, and its implications for gatherings in the coming weeks and beyond," the insurer said in the memo to staff. "Given the rapidly changing circumstances, and based on guidance from public health and government authorities, and your feedback, we’ve taken the decision to postpone ... return to our offices in North America for the time being," Manulife wrote. Separately, Toronto-Dominion Bank (TD.TO) on Friday said it was asking employees who are able to do so to work from home until further notice. "We continue to see rising COVID-19 cases as Omicron evolves to become the dominant variant around the world," the bank told staff in a memo seen by Reuters. Wall Street banks and investment firms are retrenching from their push to get staff back to the office, with Citigroup Inc (C.N), Goldman Sachs Group Inc (GS.N), Carlyle Group Inc (CG.O), Blackstone (BX.N) and MetLife (MET.N) adjusting return-to-work plans and canceling holiday parties this week. Earlier this week, JPMorgan Chase & Co (JPM.N) told unvaccinated staff in Manhattan to work from home, while investment bank Jefferies Financial Group (JEF.N) last week asked staff in Manhattan and elsewhere to again steer clear of the office due to a spate of COVID-19 cases. COVID cases have been spiking in New York and other financial hubs, while the Omicron variant has been detected in at least 77 countries, fuelling concerns that its large number of mutations is helping it spread fast and evade protection provided by COVID-19 vaccines.