* HitecVision sells CapeOmega after Solveig Gas deal
* Ministry limits ownership in "vital" gas infrastructure
* Gassled has world's largest offshore gas pipeline system (Adds Norwegian oil ministry comment on infrastructure ownership)
OSLO, April 23 (Reuters) - Swiss-based asset manager Partners Group has agreed to buy CapeOmega, a partner in Norwegian pipeline owner Gassled, from HitecVision for 1.2 billion euros ($1.35 billion), the companies said on Tuesday.
The deal will reduce HitecVision's stake in Gassled to 25.6 percent from 41.9 percent, when taking into account its acquisition of another Gassled partner, Solveig Gas earlier this month.
The deal needs approval from the Norwegian Ministry of Petroleum and Energy (MPE), which has set an ownership threshold for companies owning stakes in major gas infrastructure joint ventures.
Gassled owns the world's largest offshore gas transportation system and helps to meet about a quarter of Europe's gas demand.
"The MPE has informed all companies that they cannot expect approval from the MPE as long as their ownership share exceeds 1/3 in vital gas infrastructure joint ventures," the ministry said in an email to Reuters.
"HitecVision's agreements to acquire Solveig Gas and sell CapeOmega will be treated in a regular way by the MPE," it said.
Partners Group, which manages 73 billion euros worth of assets, said it was looking to make more acquisitions in Norway.
"Partners Group will work closely with CapeOmega's management team... to further expand in offshore infrastructure and related assets, with a focus on greenfield developments and brownfield acquisitions," Partners Group said in a statement.
Norway's oil production has declined in recent years, but the country's gas output has continued to rise along with strong demand from Britain, Germany and other European customers.
"Natural gas is increasingly adopted as a complementary fuel source to renewables in the context of the retirement of coal-fired and nuclear power plants across Europe, and the Norwegian continental shelf is poised to benefit from this demand tailwind," Partners Group said.
HitecVision, a Norwegian private equity group, declined to elaborate on the reasons for its sale.
$1 = 0.8886 euros Reporting by Nerijus Adomaitis, editing by Terje Solsvik and Jane Merriman