The United States could be willing to restrict missile deployments in Europe if Russia steps back from Ukraine's borders as the region braces for conflict, according to a leaked document published in a Spanish newspaper on Wednesday.

The daily El Pais published two documents purported to be written replies from the United States and NATO last week to Russia’s proposals for a new security arrangement in Europe. The U.S. State Department declined to comment on them.

In reference to the second document, NATO said that it never comments on "alleged leaks." But the text closely reflects statements made to the media last week by NATO Secretary-General Jens Stoltenberg as he laid out the 30-nation military organization’s position on Russia’s demands.

The U.S. document, marked as a confidential "non-paper," said that the United States would be willing to discuss in consultation with its NATO partners "a transparency mechanism to confirm the absences of Tomahawk cruise missiles at Aegis Ashore sites in Romania and Poland."

That would happen on condition that Russia "offers reciprocal transparency measures on two ground-launched missiles bases of our choosing in Russia."

Aegis Ashore is a system for defending against short- or intermediate-range missiles. But Russia has claimed in the past that the U.S. could attack its territory with Tomahawk intermediate-range missiles should they be deployed to Aegis Ashore sites. The U.S. document said Washington would have to consult with NATO allies on the potential offer, particularly with Romania and Poland.

Kremlin spokesperson Dmitry Peskov refused to comment on the leaked documents, saying only that "we didn’t release anything." In comments to the state RIA Novosti news agency, Russia’s Foreign Ministry also refused to confirm or deny that the documents published by El Pais were authentic.

Fears of a Russian invasion of Ukraine have mounted in recent months, after President Vladimir Putin deployed more than 100,000 troops to areas near Ukraine’s borders, including in neighboring Belarus, backed by tanks, artillery, helicopters and warplanes. Russian officials have insisted that Moscow has no intention of invading.

The U.S. underlined after its written proposals in the leaked document that "progress can only be achieved on these issues in an environment of de-escalation with respect to Russia’s threatening actions towards Ukraine."

In his first public remarks on the standoff in more than a month, Putin on Tuesday accused the U.S. and its allies of ignoring Russia’s central security demands but he said that Moscow is willing to talk more to ease tensions over Ukraine.

His remarks suggested that a potential Russian invasion may not be imminent and that at least one more round of diplomacy is likely.

After talks in Kyiv Wednesday with Ukrainian President Volodymyr Zelenskyy, Dutch Prime Minister Mark Rutte underlined that "it is essential for dialogue to continue." If not, Rutte, said, "it is clear that further aggression against Ukraine will have serious consequences."

Notable in its absence from the leaked documents is any mention of Ukraine’s hopes of joining NATO. Putin has demanded that NATO stop taking in any new members and withdraw its troops and equipment from countries that joined the alliance since 1997, almost half its ranks.

In the leaked document linked to NATO, the 30 allies said they "reaffirm our commitment to NATO’s Open Door policy," without specifically mentioning Ukraine. Under Article 10 of NATO’s founding treaty, other European countries may be invited in if they further the goals of European security.

At a NATO summit in 2008, NATO leaders said that they welcomed "Ukraine’s and Georgia’s Euro-Atlantic aspirations for membership in NATO," adding: "We agreed today that these countries will become members of NATO."

Russia invaded Georgia later that year, and in 2014 annexed Ukraine’s Crimean Peninsula. Around 14,000 people have been killed in the conflict that still simmers in eastern Ukraine. Their membership plans have been on hold for years, although NATO continues to support them and promote reforms.