NATO appeared to make little progress Thursday in narrowing differences with Russia over U.S. plans to install missile defenses in eastern Europe, even after the U.S. offered to delay activating the bases until there is proof of a threat from Iran.

"We cannot agree on what was offered to us, and are sticking to our position," Russian Defense Minister Anatoly Serdyukov told reporters after talks with his NATO counterparts.

However, he said talks would continue.

"It seems to me that the Americans are starting to better understand our concerns and we welcome that," Serdyukov said.

Underscoring the continuing tensions, two Russian strategic bombers neared the Dutch coastal resort where the ministers were meeting, on an unusual practice run that could be interpreted as a signal to NATO, the Norwegian military said.

Lt. Col. John Espen Lien, a Norwegian military spokesman, said two Tu-160 strategic bombers, flew a highly unusual course near the Norwegian coast and between Britain and Denmark before turning back some 120 miles northwest of the Netherlands.

"It could have been a coincidence, but there is also a chance that it was a signal," Lien told The Associated Press.

Russia has routinely been sending bomber flights from its northern bases in recent months in what is broadly seen as a demonstration of its military power 16 years after the collapse of the Soviet Union left it with few resources.

NATO officials in Noordwijk said the Russian planes remained in international airspace and were not considered threatening.

The meeting comes days after Defense Secretary Robert Gates said Washington may delay activating the proposed missile defense sites in Poland and the Czech Republic until it has "definitive proof" of a missile threat from Iran.

The announcement was widely seen as an attempt to mollify Russian opposition to the U.S. plan. Moscow says Iran is decades away from developing missile technology that could threaten Europe or North America, and claims the U.S. bases will undermine Russia's own missile deterrent force.

Russian President Vladimir Putin last week said he detected "a certain transformation" in the U.S. view that allowed for continued dialogue.

The U.S. plan would install a radar base in the Czech Republic and 10 interceptor missiles in Poland. It is part of a wider missile shield involving defenses in California and Alaska which the United States says are to defend against any long-range missile attack from countries such as North Korea or Iran.

French Defense Minister Herve Morin said European allies generally agreed with the Americans that there is a ballistic threat, "but not necessarily on the imminence of the threat."

Piqued by the U.S. plans, Russia has frozen cooperation with NATO on a separate project to develop defenses against short-range battlefield missiles. Putin has also threatened to pull out of a Cold War-era treaty controlling conventional forces in Europe.

Morin urged the Netherlands and other nations fighting the Taliban to maintain their troop levels in front-line areas of Afghanistan. But he made clear during talks with other NATO defense ministers that his nation would not be sending combat troops to assist allies in Afghanistan's dangerous south.

The Netherlands warned during the meeting's first day Wednesday that public pressure could force it to pull its 1,600 troops out of the frontline province of Uruzgan next year if they do not get more support from other allies.

That prospect has raised fears that one nation after another could pull its forces back.

"The signal that a country gives by reducing its forces could be an extremely negative sign for the totality of the countries engaged in Afghanistan," Morin said. "I would say there is an extremely great risk of a domino effect."

Morin said France would send a training unit to prepare Afghan army forces to help the Dutch and would continue to provide air support to NATO nations with troops in the south. But he said France would not be sending combat troops to the southern region.

"For us it's instructors," he said.

Before the talks with Serdyukov, NATO ministers agreed on the need to scale down a new elite force because the deployment of thousands of soldiers to Afghanistan, the Balkans, the Middle East and Africa has left the 26 nations with too few combat forces to maintain the 25,000-strong unit meant as the spearhead of the allies' military modernization drive.

NATO spokesman James Appathurai declined to say how small the new "core" force would be.