President Trump’s election this year gave Russia hope that it could restore economic and diplomatic ties with the United States while continuing to wage war in Ukraine.

On Thursday, the Kremlin made the most direct statement yet that, from its perspective, that strategy is stumbling.

“American diplomats believe that we need to directly tie the process of removing the irritants in bilateral relations with the settlement in Ukraine,” Dmitri S. Peskov, the Kremlin’s spokesman, told reporters on Friday at an annual economic conference in St. Petersburg, Russia.

Mr. Peskov reiterated the Kremlin’s position, which is that it wants to discuss relations with the United States separately from efforts to end the war in Ukraine. He said “building relations and getting rid of irritants” first between the United States and Russia would only “contribute to an early settlement in Ukraine.”

The Kremlin has been hoping that a thaw with Washington would lead to the lifting of some economic sanctions, the return of some American companies, U.S. investments in Russian natural resources and more leeway for Russia to assert its interests in former Soviet states.

At the same time, President Vladimir V. Putin of Russia has shown little interest in bending to U.S., European and Ukrainian demands to agree to a cease-fire in Ukraine, where his forces are on the offensive.

Mr. Trump had promised to end the war in Ukraine 24 hours after taking office, but efforts to mediate have been dogged by deep disagreements between the warring countries about what peace should look like.

The Kremlin insists on formal recognition of sovereignty over regions in Ukraine that it claims to be its own, but does not occupy in full — one of several positions that are unacceptable to the Ukrainian government.

After two direct meetings between Russian and Ukrainian representatives, the negotiations have led only to agreements to exchange prisoners of war and bodies of fallen soldiers.

Frustrated by the lack of progress, Mr. Trump has his diplomatic attention elsewhere, most recently the conflict between Iran and Israel, where he is considering whether to join the war on the side of Israel.

Meanwhile, Russian air assaults on Ukraine have intensified in recent weeks, dimming any hopes for a cease-fire. On Thursday night, Russia launched drone attacks on Odesa and Kharkiv, injuring 20 people and killing one person in Odesa, President Volodymyr Zelensky of Ukraine said on Facebook.

Mr. Peskov said that Russia expected Russian and Ukrainian representatives to set a date for their third meeting next week, but that the Kremlin was determined to achieve its stated goals in Ukraine either diplomatically or militarily.

The talks between Russia and the United States on restoring bilateral ties have also been dragging. Despite multiple phone calls between Mr. Putin and Mr. Trump this year and at least four public meetings of Russian and American officials over the same period, nothing substantive has been achieved so far on that issue. The two countries’ diplomatic missions are still understaffed and some consulates are still shut.

There has also not been any tangible movement in terms of American companies returning to Russia or sanctions being lifted. The St. Petersburg conference, a yearly event promoted by the Kremlin as a magnet for Western businesses, has turned into a platform where Russian state companies showcase themselves. Again this year, no major American investors showed up and there was little sign of Western interest.

For instance, Mr. Putin, who is expected to speak later on Friday, did not meet with international business leaders as he did in prior years.

Kim Barker in Kyiv and Anatoly Kurmanaev in Berlin contributed reporting.