NATO will push at its May summit for members to keep up their commitments to international security in spite of hard economic times, its secretary general said Thursday.

Anders Fogh Rasmussen spoke after meeting with Spanish Prime Minister Mariano Rajoy, who is overseeing emergency budget cuts, including nearly nine percent on defence spending.

Rajoy said Spain will review its contribution to NATO's support for Afghanistan after the alliance transfers security to Afghan forces in 2014.

Rasmussen said that at a summit of NATO leaders in Chicago on May 20 and 21, "We will discuss how to provide security in a time of economic austerity."

Discussions will include the cost of continuing to provide other support for Afghanistan after the security handover.

"NATO will pay its fair share but it's important that the whole international community and the Afghans themselves play their part because it is in the interests of all of our security," he said.

"When most budgets are cut, defence spending can't be exempt, but when economic times are hard security challenges don't get any easier," Rasmussen said.

"In Chicago we will show the way forward so that we can deal with the security challenges of tomorrow with the economic resources of today by working better together."

He cited projects such as a European anti-missile defence shield, which Spain has supported by allowing installations to be built on its soil.

Rajoy reaffirmed Spain's commitment to the mission due to wind down in 2014 in Afghanistan, where it has nearly 1,500 troops serving in a NATO force fighting Taliban insurgents.

Discussions at the Chicago summit "will determine the model for our contribution" to supporting Afghanistan after 2014, he said.

"It will have to have a solid political base and will have to be quantitatively and qualitatively different from the current mission," he said, without elaborating.