Kyiv: Senior Ukrainian officials visited Washington on Tuesday to seek US support against Russia while accusing Moscow of dragging its feet at peace talks.

Kyiv showed its ability to continue fighting by setting off an explosive device under a bridge that has become a symbol of the Kremlin's claims on Ukrainian territory.

President Volodymyr Zelenskiy said a Russian artillery strike killed four people in the northern Ukrainian city of Sumy, an area where Russian forces have been making advances.

Zelenskiy's chief of staff, Andriy Yermak, writing on Telegram after meeting US Ukraine envoy Keith Kellogg, accused Russia of "playing for time, manipulating the talks, trying to avoid US sanctions and not wanting a ceasefire."

Ukrainian Foreign Minister Andrii Sybiha was more blunt, saying Russia had ignored a request to comment on Ukraine's proposals at Monday's second round of direct peace talks in Istanbul. "We demand Russia’s reply. Each day of silence from them proves their wish to continue the war," Sybiha wrote on social media. Russia, he said, had "passed a set of old ultimatums that do not move the situation any closer to true peace."

Yermak, in the United States with Deputy Prime Minister Yulia Svyrydenko, also said he briefed US envoy Steve Witkoff "on the real situation on the battlefield" and invited him to visit Ukraine "to witness the situation firsthand. We need a ceasefire, we have fully supported the US proposal on this since March. We are also ready for a leaders’ meeting, which Russia continues to avoid," he said.

A US official said Yermak was scheduled to meet with US Secretary of State Marco Rubio on Wednesday. Yermak said officials would also discuss a deal that gives the US preferential access to new Ukrainian mineral projects and sets up an investment fund that could be used for reconstruction.

Monday's talks in Istanbul made little headway toward ending Russia's war in Ukraine, apart from an exchange of proposals and an undertaking to conduct a new large-scale swap of prisoners of war. Moscow has responded to accusations of foot-dragging by saying Ukraine is not making a genuine effort to seek peace.

At the talks, Russia told Ukraine it would agree to end the war only if Kyiv gives up big new chunks of territory and accepts limits on the size of its army. Ukraine rejects the Russian conditions as tantamount to surrender. "The (peace) settlement theme is extremely complex, it consists of a large number of nuances...," said Kremlin spokesman Dmitry Peskov, adding that "it would be wrong to expect any immediate solutions and breakthroughs here".

It was unclear what the next step in negotiations between Russia and Ukraine would be, but Moscow said early on Wednesday that Istanbul would remain the venue for future talks.

Coordinated Attacks
Kyiv launched in recent days what appeared to be one of its biggest waves of coordinated attacks in the conflict.

Ukraine's SBU security service said it had hit a road and rail bridge that links Russia and Crimea below the water level with explosives. The extent of any damage was not clear and Russian officials later said vehicle traffic had resumed. The bridge is a flagship project for Russian President Vladimir Putin, built after he annexed Crimea from Ukraine in 2014, a precursor to the latest conflict.

Russian officials also announced that emergency crews had restored power to some 700,000 customers in Russian-controlled areas of southern Ukraine, in Zaporizhzhia and Kherson regions, after drones and shelling had knocked out substations and other infrastructure.

Ukraine's attack on Russian-occupied territory in the Zaporizhzhia and Kherson regions followed multiple Russian attacks on Ukrainian energy infrastructure that have at times left millions of Ukrainians without power. The latest attacks followed drone strikes over the weekend on Russian military airfields, some of which housed long-range nuclear-capable bombers.

Ukraine's success in striking deep into Russia has prompted calls by some Russian military bloggers for a harsh response.

Zelenskiy denounced the Russian military strike on Sumy, describing the incident as: "all one needs to know about the Russian wish to end this war." He also announced a military shakeup, including the appointment to a new post of a commander who resigned over a deadly Russian attack on a training area.

Zelenskiy, speaking in his nightly video address after a meeting of top commanders, said the reshuffle sought to ensure that the military remained focused on combat more than three years after Russia's invasion of its smaller neighbour.