Ukrainian President Volodymyr Zelenskyy says the country has been holding talks with a number of countries on security guarantees. Ukraine signed such a pact with Britain last week.

Zelenskyy said in a video address on Sunday that negotiations with Romania have begun.

The president met with British Prime Minister Rishi Sunak in Kyiv on Friday. The leaders signed an agreement on long-term security support for Ukraine.

Zelenskyy's remark comes as some observers point to flagging support for Ukraine among Western countries.

The United States, Ukraine's biggest backer, faces a stalemate in Congress over an emergency spending bill to continue military assistance to Ukraine.

Zelenskyy is apparently trying to stress that the US and European countries are committed to supporting his country.

Meanwhile, a US think tank, the Institute for the Study of War, on Sunday quoted Russian sources as saying that Russia's military is preparing to launch a new offensive in the coming weeks when the ground freezes in eastern and southern Ukraine.

Ukraine remains on alert as Russia is stepping up its offensive in the eastern region of Kharkiv and other areas, claiming that Ukraine's counteroffensive has failed.