POTI, Georgia — Russian forces dug trenches and built fortifications in key areas of Georgia Thursday, but also rolled columns of tanks north toward home, picking and choosing how their nation would comply with the terms of a peace accord.

A top Russian general said it could be more than 10 days before the bulk of the troops return to Russia.

Although Russian President Dmitry Medvedev has promised that his forces would pull back as far as separatist Ossetia and a surrounding zone by Friday, Russian troops appeared to be in no hurry — even settling down in strategic spots. This raised concerns about whether Moscow was aiming for a lengthy occupation of its smaller, pro-Western neighbor.

An EU-sponsored cease-fire requires both Russian and Georgian forces to move back to positions held before fighting broke out Aug. 7 in Georgia's separatist republic of South Ossetia, which has close ties to Russia. The Russians are allowed to remain in zones around Georgia's borders with South Ossetia and another separatist region, Abkhazia.

The war in Georgia, a small country straining to escape Moscow's influence, has sent tensions between Moscow and the West to the highest levels since the 1991 breakup of the Soviet Union.

NATO, Russia's Cold War foe, said it had received a note from Moscow announcing that Russia is halting military cooperation with the trans-Atlantic alliance.

On Wednesday, Secretary of State Condoleezza Rice and her Polish counterpart signed a deal to build an American missile defense base in Poland after a top Russian general warned last week that Poland was risking an attack, possibly a nuclear one, by developing the base.

Russian forces took up positions Thursday at the entrance to Georgia's main Black Sea port city of Poti, excavating trenches, setting up mortars and blocking a key bridge with armored personnel carriers and trucks. Another group of APCs and trucks were positioned in a wooded area nearby.

But top officials in Moscow insisted troops were moving out in accordance with the EU accord.

"The pullback of Russian forces is taking place at such a tempo that by the end of Aug. 22, they will be in the zones of responsibility of Russian peacekeepers," Col.-Gen. Anatoly Nogovitsyn, the deputy head of the general staff, said at a briefing in Moscow.

Russian Defense Minister Anatoly Serdyukov reiterated that timetable late Thursday, saying a withdrawal of non-peacekeping troops into South Ossetia would begin Friday morning and be done by day's end.

An Associated Press cameraman was threatened by armed Russian troops near Poti, who stripped his video from his camera.