By Marcin Goettig and Christian Lowe

WARSAW (Reuters) - NATO member states are close to reaching consensus over steps to beef up the alliance's military presence in eastern Europe in response to Russia's intervention in Ukraine, Polish Foreign Minister Radoslaw Sikorski said on Wednesday in an interview.

Sikorski told Reuters he believed the Kremlin could still invade eastern Ukraine, though he said the possibility of Russian troops entering under cover of a humanitarian aid convoy now heading towards the Ukrainian border had receded somewhat in the past few days.

Poland, the biggest of the former Communist states to join NATO after the end of the Cold War, has been a leading voice in calling for sanctions on Russia and for NATO to shift troops and equipment eastwards to reassure members on Russia's flanks.

NATO's leadership has proposed pre-positioning supplies and equipment at bases in the east in readiness for sending troops if needed, and said one option was to enhance an existing NATO regional headquarters in north-western Poland.

"Until this year we did not have war between two of our neighbors, and now we do. So our perception of the need for reassurance is even higher," Sikorski said in the interview.

"We've welcomed the proposals by the military authorities of the alliance who have formulated what they think a reasonable reassurance package is, and we believe that's a good proposal."

He said he did not want to go into details about what the likely options were, because diplomats and military officials needed more time to prepare a consensus view that can be approved at a Sept. 4 NATO summit in Wales.

Asked how close alliance members were to reaching that consensus, Sikorski said: "I think we're quite close," and that it should be achieved in time for the summit.

The proposals under consideration by NATO fall well short of what Sikorski himself had earlier proposed, for the alliance to permanently station two brigades in eastern member states.

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Some NATO members have resisted increasing the alliance's military presence in the east.

FROZEN CONFLICT

Sikorski, who is Poland's nominee for the soon-to-be-vacant post of the European Union's chief diplomat, said it was a positive sign that Moscow has been negotiating with Kiev and the Red Cross over sending aid into eastern Ukraine.

Several EU leaders have warned the planned Russian aid convoy on its way to the border with Ukraine could have been used as a cover for a military attack. Russia denies any such intention.

The fact that Russia is talking with others about the convoy means "there is hope the whole initiative will be put within some kind of agreed procedures," said Sikorski, who was educated at Britain's Oxford University.

However he cautioned that "a negative scenario" with the convoy could still be played out.

He had previously said Russia had stationed large numbers of troops on its border with Ukraine because it either wanted to pressure the Western-backed government in Kiev, or because it wanted to attack.

Asked if this was still his view, Sikorski replied: "Yes," though he said only Russian President Vladimir Putin knew what Moscow's next move would be.

He said he believed Putin's latest strategy was to foment in eastern Ukraine a "frozen conflict" similar to the one in Moldova's Transdniestria region, which has for decades now been controlled by Moscow-backed separatists.

The aim is "to distract Ukraine from implementing the association agreement (with the EU) and thereby making it more difficult for Ukraine to become a successful free market democracy," Sikorski said.

Polish farmers have warned of heavy losses after Russia, a major importer of Polish agricultural produce, responded to new EU sanctions by imposing an embargo on imports of many food items from Europe.

"We knew all along that, having a much higher proportion of trade, exports to Russia than other countries, double the rate of Germany for example, we would pay a higher price, which is why we were not gung-ho about sanctions," Sikorski said.

Asked if, despite the cost, Poland would stand firmly by the sanctions on Russia, he said: "Sure, of course."

(Writing by Christian Lowe; Editing by Raissa Kasolowsky)