Russian and US teams have held six hours of talks in Turkey to try to restore normal functioning of their embassies.
Russia's President Vladimir Putin said that initial contacts with US President Donald Trump's government had inspired hope.
The talks, focused narrowly on conditions for each other's diplomats, provided an early test of the two countries' ability to reset wider relations, amid a Trump administration outreach effort that has alarmed European allies and Ukraine.
Last year, Russia described relations as "below zero" under the administration of then US president Joe Biden, who backed Ukraine with aid and weapons and imposed sanctions on Russia to punish it for its invasion in 2022.
But Mr Trump, who has promised a quick end to the war, upended US policy swiftly to open talks with Moscow, beginning with a phone call to Mr Putin on 12 February and a high-level diplomatic meeting in Saudi Arabia six days later.
Russian state news agency TASS said the talks in Turkey, held at the residence of the US consulate general in Istanbul, wrapped up without any statements to the media.
Ukraine and its European allies are worried that President Trump's rapid rapprochement with Russia could lead to a deal on ending the war that sidelines them and undermines their security.
The US leader has said that he wants to end the bloodshed with an early ceasefire.
President Putin this week tempered expectations of a quick deal, saying trust between Russia and the United States had to be rebuilt before anything could be achieved.
But in televised comments to members of the FSB security service today, he said: "I note that the first contacts with the new American administration inspire certain hopes".
"There is a reciprocal mood to work to restore intergovernmental ties and to gradually resolve the huge number of systemic and strategic problems that have built up in the world's security architecture."
Russian Foreign Ministry spokeswoman Maria Zakharova said the Turkish talks were expected to be the first in a series of contacts aimed at building confidence and removing "irritants" in bilateral relations.
The US State Department said the discussions would cover issues such as staffing levels, visas and diplomatic banking.
"To be clear, there are no political or security issues on the agenda. Ukraine is not on the agenda," a department spokesperson said before the meeting.
"The constructiveness of these talks will become apparent very quickly; either issues will get resolved or they won't. We will know soon if Russia is really willing to engage in good faith."
Russia and the US have expelled diplomats and limited the appointment of new staff at each other's missions in tit-for-tat measures over the past decade, leaving their embassies thinly staffed.
Russian Foreign Minister Sergei Lavrov said the outcome of the meeting "will show how quickly and effectively we can move".
He acknowledged that Russia had "created uncomfortable conditions" for US diplomats in Moscow, in what he said was retaliation for Washington's treatment of Russian diplomats.
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In an example of judicial cooperation, Moscow said the US has deported Dmitry Koshelev, wanted by Moscow on suspicion of stealing $1.5 million (€1.8m) at gunpoint from a courier at St Petersburg's Pulkovo Airport in 2014, while dressed as a member of Russian special forces.
In a statement, Russia's prosecutor general said that he would arrive in Moscow via Cairo.
Despite their narrow focus, the talks could eventually lead to progress over the whole Russia-US relationship in areas such as nuclear disarmament and economic cooperation.
Both sides see potential for lucrative business ventures.
President Putin said this week that Moscow would be ready to invite the US to enter joint projects to mine rare earth deposits in Russia and the parts of Ukraine that it has claimed as its own.
Kremlin spokesman Dmitry Peskov said there could be joint development of natural resources in the Arctic Circle, though there were no substantive talks on this yet.
The US delegation in Istanbul was led by Deputy Assistant Secretary of State Sonata Coulter, and the Russian team by Alexander Darchiyev, head of the foreign ministry's North America department.
Mr Darchiyev is seen as front-runner to be Russia's next ambassador to the US, a post now vacant.
Annexed Ukrainian territory 'non-negotiable' - Moscow
Russia has ruled out any negotiation over the status of five Ukrainian regions it claims to have annexed despite not fully controlling four of them.
"The territories which have become subjects of the Russian federation, which are inscribed in our country's constitution, are an inseparable part of our country. This is undeniable and non-negotiable," Kremlin spokesperson Dmitry Peskov said.
Meanwhile, the European Union has invited Ukraine's President Volodymyr Zelensky to a special leaders' summit on 6 March, to discuss future support to Ukraine.
"The EU and its member states are ready to take more responsibility for Europe's security," European Council President Antonio Costa said.
"We should therefore be prepared for a possible European contribution to the security guarantees that will be necessary to ensure a lasting peace in Ukraine."
Mr Costa, who chairs the summits, said he aimed for decisions that would make the EU "better equipped to deal with immediate and future challenges to its security".
