Fifteen of 18 analysts predicted a reduction of 25 basis points when the seven-member board meets on Friday, while three said policymakers would trim the rate by 50 basis points to 6 percent.

A cut would mark the fifth reduction in an easing cycle meant to bolster Latin America's fourth-largest economy, which was hit hard by the global fall in prices for crude oil as it also struggled with high inflation.

Gross domestic product growth for the first quarter was below central bank predictions of 1.3 percent when released last week, coming in at 1.1 percent compared to the same quarter last year.

But the weaker-than-expected expansion numbers would not necessarily motivate policymakers to vote for a sharper cut, analysts said.

"On May's policy meeting, we expect the bank to deliver a 25 basis point cut to 6.25 percent," Nomura analyst Mario Castro said in a note to investors. "In fact, despite the weak growth numbers, we expect the bank to return to more cautious easing (after its 50 basis point cut to 6.5 percent in April) given the challenges on the inflation side."

A split vote was likely, those surveyed said.

"The decision will be by majority, because for some members inflation risks are still possible, but the more-than-expected economic deceleration will dominate the decision," said Angela Gonzalez, analyst at Itau.

Inflation expectations for the close of this year were up to 4.45 percent, from 4.40 percent in April's poll. Predictions for 2018 inflation were steady at 3.5 percent.

May consumer prices will rise 0.30 percent, taking 12-month inflation to 4.44 percent, above the bank's target range of 2 percent to 4 percent.

Growth expectations for this year were down to 1.8 percent, compared to the 2.02 percent in April's poll. Predictions for 2018 were down to 2.55 percent, from 2.8 percent.

The central bank's technical team had predicted year-on-year expansion between 0.8 percent and 1.8 percent for 2017, with 1.3 percent as the most likely figure.