* Adds 20 new routes for winter 2017/18
* To start with four routes next month
* Further encroaches into Lufthansa territory
* Lufthansa considers offering budget flights from Frankfurt (Adds CEO comments)
FRANKFURT, Feb 28 (Reuters) - Irish low-cost carrier Ryanair is ramping up its expansion at Frankfurt airport with 20 new routes and the deployment of seven planes at the home of German rival Lufthansa.
Ryanair is starting with two aircraft flying to four tourist destinations in Spain and Portugal from next month, but new routes from October include London, adding to pressure on traditional carriers serving business passengers on that route.
"We want to attract more and more business passengers to fly from Frankfurt," Ryanair CEO Michael O'Leary told journalists at the airport on Tuesday.
Ryanair's push into Frankfurt has prompted Lufthansa to look at using its own budget carrier, Eurowings, for flights from its main hub from 2018, against previous expectations.
"The boardroom of Lufthansa is the only place in Europe where people think that Eurowings is low-cost," O'Leary said on the prospect of such a move by Lufthansa.
The new Ryanair winter routes from Frankfurt also include Glasgow, Manchester and more traditional tourist destinations such as Gran Canaria and Tenerife, Ryanair said.
The company has previously flown from Hahn airport, about 120km from Frankfurt, but has been increasing its presence at primary airports as it seeks more business passengers and tries to boost passenger numbers to 200 million a year by 2024.
It carried 119 million people last year, overtaking Lufthansa Group as Europe's largest airline in terms of passenger numbers.
Ryanair is also seeking deals to provide short-haul "feeder flights" to link passengers to routes operated by long-haul carriers and plans to start serving low-cost operator Norwegian Air Shuttle from April, O'Leary said.
The Irish airline has also offered to provide feeder flights for Portugal's TAP but talks have ceased. Air France and Lufthansa have both said in the past that they are not interested in having Ryanair provide feeder flights.
Reporting by Maria Sheahan; Writing by Victoria Bryan; Editing by Michelle Martin and David Goodman