Dec 19 (Reuters) - Citigroup Inc will relocate its global headquarters to lower Manhattan as part of a $1 billion lease and renovation deal, Crain's New York Business reported on Thursday.

According to Crain's, the bank would move from 399 Park Avenue in New York City, where it has been based for decades, to Greenwich Street, where Citigroup signed a more than $1 billion deal to renew its lease plus gut and renovate a twin-building complex that it already occupies at 388 and 390 Greenwich Street.

The deal is a major victory for landlord SL Green, which had competed for months to hold onto Citi as a tenant. Combined, 388 and 390 Greenwich Street is the largest single property that SL Green owns, Crain's said.

SL Green confirmed the lease extension in a press release, while Citigroup declined to comment.

As per the agreement, Citi has the option to extend its 2.7 million-square-foot lease by at least 15 years at the two properties when it expires in 2020 or exercise a right to acquire the buildings for around $2 billion, Crain's reported.

Citi is expected to undertake a makeover of the interior spaces and possibly a remake of the exterior with a new skin of glass of the two properties, which were built in the 1990s, Crain's said. ()

Citi was represented in the deal by a leasing team from CBRE Group Inc and by a legal team from the law firm Fried Frank.