The 11th-hour funding bill passed by Congress on Saturday will keep US federal agencies running for another 45 days, but left out new aid to Ukraine amid opposition from some hardline Republicans.

"The Ukrainian government is now actively working with its American partners to ensure that the new US budget decision, which will be developed over the next 45 days, includes new funds to help Ukraine," Kyiv's foreign ministry spokesman Oleg Nikolenko said.

Ukrainian defence chief Rustem Umerov later said he spoke with US counterpart Lloyd Austin to discuss further military aid after the decision.

"Secretary Austin assured me that US support to Ukraine will continue. Ukraine's warriors will continue to have a strong back-up on the battlefield," Umerov said on social media.

Kyiv has relied heavily on Western support since Russia invaded last year.

The United States has been the country's biggest financial backer, providing it with over $40 billion in military assistance.

But the issue of funding for Ukraine has become increasingly politicised in Washington, where some Republican lawmakers have pushed for deep spending cuts.

Ukraine held a weapons forum this week to attract more manufacturers to build arms in Ukraine, amid concerns arms support from its Western allies may waver.