Cardiff, Sep 4 (IANS): Western leaders meeting for a NATO summit in Wales Thursday criticised Russia for its "destabilising" influence on the crisis in Ukraine.

NATO and Britain warned that pressure on Russia would be raised if it did not change course in eastern Ukraine, BBC reported.

Ukraine's President Petro Poroshenko was to brief US and EU leaders on earlier discussions on a ceasefire plan with Russian President Vladimir Putin. Some 2,600 people have died in fighting between Ukrainian troops and pro-Russian rebels.

The two-day 26th NATO summit in Wales is the first in Britain since erstwhile British prime minister Margaret Thatcher welcomed to London the leaders of the 28 NATO member-countries in 1990, Xinhua reported.

Also NATO's tasks in Afghanistan, the rise of extremism and sectarian strife in the Middle East and North Africa were expected to top the summit agenda.

The alliance will also discuss newer threats such as cyber security and hybrid warfare.

Representatives from the UN and the European Union will also attend the meeting, together with officials from the International Security Assistance Force (ISAF) in Afghanistan.

The last NATO summit was held in Chicago, in the US, in 2012.