Talks between the US and Ukrainian delegations in Florida on ending the war with Russia are "not easy", a source close to the Kyiv delegation told AFP on Sunday.
"The process is not easy, because the search for formulations and solutions continues," said the source, adding that the exchanges had nevertheless been "constructive".
"Everyone is interested in a practical result so that there is a subject for further negotiations between the US and Russia," the source added.
Ukraine's military leadership had joined a closed session on specific issues, said the source.
Another source briefed on the developments told AFP: "The Americans really want the final points to be agreed upon (in the current talks) so that they can go to Moscow.
"The wording is complicated, especially with regard to territories, because they see themselves exclusively as mediators, not as a party" supporting Ukraine, the source added.
"But everyone is trying to be constructive and find a solution."