Nov 4 (Reuters) - Realty Income Corp ( O ) raised the

lower end of its annual funds from operations (FFO) forecast on

Monday, citing a positive investment environment.

The rising competition among retailers is fueling a surge in

demand for commercial space, benefiting real estate investment

trusts (REITs) such as Realty Income ( O ), which counts Walgreens

and Dollar General ( DG ) among its customers.

"Supported by improvements in the investment environment and

solid operating results, we see a robust pipeline of

opportunities," said CEO Sumit Roy.

The REIT now expects its full-year adjusted FFO to range

between $4.17 and $4.21 per share, up from its previous estimate

of $4.15 to $4.21 per share.

The company also lifted its full-year investment volume to

an estimated $3.5 billion, up from its previous figure of $3

billion.

Realty Income ( O ), which recently closed a $9.3 billion merger

with Spirit Realty Capital, owns over 13,000 properties in the

United States and leases them to clients across the retail,

restaurants and gaming industries.

The company's same-store rental revenues for the quarter

ended September 30 increased by 0.2% to $1 billion, compared

with the same period last year.

Total quarterly revenue rose 28% to $1.33 billion, beating

analysts' average expectation of $1.28 billion, according to

data compiled by LSEG.

The San Diego, California-based company posted an adjusted

FFO of $1.05 per share for the third quarter, falling short of

analysts' estimates of $1.07 per share.