The head of NATO called on China and Russia on Thursday to help fund Afghan security after 2014, as the alliance tries to rally contributions from a wider range of sources before most foreign combat troops pull out of Afghanistan.

NATO estimates that the annual cost of maintaining Afghan security forces will be some $4 billion (2.5 billion pounds), and the United States is hoping for contributions worth 1 billion euros ($1.3 billion) from other NATO allies and partners. But so far only Britain has publicly pledged an actual amount of cash, $110 million a year.

We would welcome financial contributions from Russia, China and other countries to ensure a strong sustainable Afghan security force beyond 2014, Secretary General Anders Fogh Rasmussen told a news conference in Brussels, where NATO foreign and defence ministers were meeting to prepare for a summit next month in Chicago.

The United States and NATO, keen to douse fears Afghanistan could face renewed civil war when foreign troops pull out, want to use the summit to demonstrate a long-term commitment to Afghan stability that will endure well after 2014.

China has significant economic stakes in Afghanistan and is also a close ally of neighbouring Pakistan, making it potentially a strong partner in helping to foster stability.

With the world's biggest foreign exchange reserves, it is also better placed than many western countries struggling with economic downturn to help pay for stability in Afghanistan.

Analysts have suggested, however, that China would be wary of becoming too sucked in to problems in Afghanistan, and would not want to be seen to taking sides if this were to make it a target for Islamist militants.

The Chinese officials I have asked about financing Afghan security forces have been sceptical, saying they'd rather provide support on the civilian and economic side, said Andrew Small at The German Marshall Fund of the United States.

On Thursday, NATO ministers met Russian Foreign Minister Sergei Lavrov, and tried to narrow differences with Russia over Syria, Afghanistan and missile defence - all areas where NATO allies would like Russian support to promote stability.

Lavrov did not respond at the meeting to Rasmussen's request for financial help, according to a western diplomat familiar with the talks.

But Russia's cooperation with western troops in the International Security Assistance Force (ISAF) is expected to expand soon. Currently Russia allows ISAF to use a rail route through Russian territory to transport equipment.

Rasmussen said Russia had offered the use of a new transit route, which will allow ISAF to send supplies in and out of Afghanistan using both the Russian rail network and air transport. The route is expected to pass through the town of Ulyanovsk, said two officials, one in Russia and one in Brussels.

The United States and its allies have been building up alternative routes in and out of Afghanistan, reducing its dependence on Pakistan, which suspended supply routes after a NATO cross-border air attack in November killed 24 Pakistani soldiers.

However, despite the progress on expanding supply routes through Russia, President-elect Vladimir Putin is likely to turn down an invitation from NATO to attend the Chicago summit.

I have talked with President-elect Putin, and we agreed that due to a very busy domestic political calendar in Russia, just a few weeks after his inauguration as a new president of Russia, it's not possible and not practical also to have a NATO-Russia Summit meeting in Chicago, Rasmussen said.

Russian diplomats have said Putin was unlikely to attend in the absence of an agreement bridging deep differences over U.S. and NATO plans for a European anti-missile shield.

Lavrov repeated complaints over the missile defence system, which Russia says risks tipping the balance of nuclear power between itself and the United States in NATO'S favour. NATO says the shield is meant to protect against a potential Iranian threat and not against Russia.

We need clear guarantees that it is not targeted against us, Lavrov said.

(Additional reporting By Arshad Mohammed; Editing by Myra MacDonald)