WARSAW (Reuters) - New NATO secretary-general Jens Stoltenberg said on Sunday that the Western alliance could deploy its forces wherever it wants, apparently calling into question post-Cold War agreements that have been shaken by Russia's actions in Crimea and Ukraine.

Stoltenberg was visiting NATO member Poland to reassure it that NATO would provide the protection it sought against its former communist master, Russia, which in recent months has annexed the Crimean Peninsula from Ukraine, and been accused by the West of sending troops and equipment to back pro-Russian rebels in eastern Ukraine.

At a summit a month ago, NATO leaders agreed to set up a "spearhead" rapid reaction force that could be sent to a hotspot within days, and to pre-position equipment and supplies in eastern European countries to receive the force if needed.

But they rejected appeals from NATO members in Eastern Europe, including Poland, to station thousands of troops there permanently -- partly because of the expense, and partly because they did not want to break a 1997 pact under which NATO promised Russia it would not permanently station significant combat forces in the east.

Stoltenberg appeared to take a tougher line in Poland, however.

"Next year, at the ministerial meeting, we will take decisions regarding the so-called spearhead but, even before it is established, NATO has a strong army after all. We can deploy it wherever we want to," Stoltenberg told the state broadcaster TVP Info.

"These capabilities already exist. We have them, and we can deploy them in individual regions. And this is only an add-on to what the alliance already has."

Stoltenberg, a former Norwegian prime minister, took over on Wednesday as NATO secretary-general, at a time when the alliance is wrapping up its combat mission in Afghanistan but faces new challenges from a resurgent Russia to the east and from Islamic State militants on the borders of Turkey, NATO's southernmost member.

NATO has made clear it will not intervene militarily in Ukraine, which is not an alliance member, but has reinforced the defenses of its eastern member states. Russia has repeatedly denied sending forces or equipment to the rebels in eastern Ukraine.

(Reporting by Anna Wlodarczak-Semczuk; Writing by Marcin Goclowski; Editing by Kevin Liffey)