Russia "does not object to another extension of the 'Black Sea Initiative' after its second term expiration on March 18, but only for 60 days," Vershinin said.
The deal, which was extended for 120 days in November, is up for renewal on Saturday.
"Our further stance will be determined upon tangible progress on normalization of our agricultural exports, not in words, but in deeds," he added.
In a statement after talks with U.N. trade official Rebeca Grynspan and aid chief Martin Griffiths, Vershinin said that despite a "comprehensive and frank conversation," Russia noted that restrictions on its agricultural exporters remained.
A senior Ukrainian government official involved in the talks to secure the initial deal said Kyiv considered a 60-day extension to be in violation of the agreement's terms.
"The agreement clearly states that extensions are possible for a minimum of 120 days," he told Reuters. "To extend it for 60 days, you have to amend the deal."
U.N. spokesman Stephane Dujarric told reporters in New York following the talks: "We're doing everything to preserve the integrity and ensure the continuity of the agreement,"
He said the U.N. was working with Russia, the private sector, the European Union, Britain, the United States and others to facilitate Moscow's agricultural exports, adding that "obviously a lot of these things are not within the decision-making powers for the United Nations."
European traders said uncertainty about the talks, especially the statement that Russia only sought an extension for 60 days, was a factor behind sharp rises in prices on the Paris Euronext wheat market.
Moscow had previously signalled it would only agree to an extension if restrictions affecting its own exports were lifted, but many diplomats and senior officials, including Turkish Defense Minister Hulusi Akar, said ahead of the talks they were optimistic the deal would be renewed.
