The IMF delayed the board decision on the loan installment, which had been due on Monday, "to allow our staff time to assess implications of various recent developments for the program," IMF spokesman Gerry Rice told reporters.

Fund staff are now engaged in "constructive discussions" with authorities in Kiev, and "we expect to announce a new board date soon," he said at a briefing.

Rice declined to specify the new developments, but Ukrainian President Petro Poroshenko this week blamed the loan payment delay on the "absolutely irresponsible" trade blockade imposed on Russian-backed rebel-held eastern regions by the country's politicians.

The pro-Western leadership in the former Soviet nation took the drastic step last week after insurgents that it has been battling since 2014 seized dozens of Ukrainian-owned businesses in response to a trade blockade by nationalist protesters.

The IMF in early March agreed on the next stage of the oft-delayed, $17.5 billion loan program, but it still requires board approval.

But Rice said delays in board meetings were not unusual, so "I wouldn't read too much into it."

The rescue program, first agreed in 2015, has seen delays previously due to the government's failure to implement reforms.