(Adds reaction to von der Leyen's letter from Greek Prime Minister, EU diplomat)
By Philip Blenkinsop and Kate Abnett
BRUSSELS, Oct 5 (Reuters) - European Commission President Ursula von der Leyen will suggest to EU leaders meeting this week how the EU could cap gas prices in a bid to contain soaring energy costs.
EU governments have debated a gas price cap for weeks, without reaching agreement. While a majority of EU members support some form of cap to tackle soaring inflation, Germany, Denmark and the Netherlands are opposed, citing concerns over security of supply.
The EU executive's chief laid out her proposals in a letter on Wednesday to EU country leaders, who will discuss whether or how to cap gas prices at a meeting in Prague on Friday.
"We should consider a price limitation in relation to the TTF in a way that continues to secure the supply of gas to Europe and to all Member States," her letter said, referring to the Dutch Title Transfer Facility (TTF) gas price.
Such a cap would be a temporary fix while the EU works on a new gas price benchmark, von der Leyen said.
Brussels says a new index is needed since the main TTF benchmark is guided by pipeline supply and no longer representative of a market that includes more liquefied natural gas.
Greek Prime Minister Kyriakos Mitsotakis welcomed von der Leyen's proposal on Twitter as "a very important step in the right direction".
One senior EU diplomat expressed scepticism however, saying it would be difficult to design a measure suited to all 27 EU countries' national energy markets.
Russia has slashed gas deliveries to Europe since its invasion of Ukraine, blaming the supply cuts on western sanctions imposed over the invasion.
Von der Leyen said the EU should also consider a price cap on gas used to generate electricity - but that any cap must be matched with tougher requirements to cut gas demand, to ensure gas consumption does not rise at a time when the fuel is scarce.
Speaking in the European Parliament on Wednesday morning, von der Leyen said the EU should also try to negotiate a price "corridor" on gas imports from trusted suppliers.
Von der Leyen said the EU should consider extra funding sources to ensure all member countries can invest enough to weather the energy crisis.
The Commission has said it is in talks with Germany about its 200 billion euro ($198.8 billion) support package that critics say threatens to distort competition in the bloc. ($1 = 1.0058 euros) (Reporting by Philip Blenkinsop, Bart Meijer and Kate Abnett; editing by Barbara Lewis, Alexandra Hudson, Kirsten Donovan)