ZURICH, Jan 14 (Reuters) - Partners Group's assets under management grew 11% to $109.1 billion last year and it expected gross client demand of $16-20 billion in 2021, it said on Thursday.

The Swiss-based investment manager received $16 billion in new commitments from clients last year, it said in a statement.

Total assets under management rose to $109.1 billion as of Dec. 31, representing net underlying assets under management growth of 11%, excluding currency swings, Partners Group said.

"For 2021, Partners Group expects gross client demand of $16 to 20 billion, together with around minus $9.5 billion in tail-down effects from the more mature closed-ended investment programmes and redemptions from evergreen programmes," the company said.

It based the 2021 fundraising outlook on the expectation that current uncertainties around the COVID-19 pandemic would improve as the year progressed, but said its platform was well-positioned to generate sustainable returns in any event.

(Reporting by Silke Koltrowitz; Editing by Michael Shields)