Sergei Ryabkov said after talks in Moscow with US Under Secretary of State Victoria Nuland that there is a risk of a further sharpening of tensions.
Meanwhile, Nuland's meetings with Russian officials have been "useful," US State Department spokesperson Ned Price said at a briefing for reporters, adding that US stance on the staffing of US missions in Russia remained "firm."
He said that the US expects parity on staffing numbers and visa reciprocity. There must be fairness, there must be flexibility on the Russian side, if both are to achieve an equitable agreement.
Price added there will be another round of talks at a lower level and that Washington hoped to find a resolution to the ongoing dispute.