Washington (CNN) Secretary of State Rex Tillerson will attend a NATO summit on March 31, according to a State Department official, after originally planning to skip the international gathering.

Earlier this week, the State Department announced that the top US diplomat would be missing the event, at that time scheduled to take place in April, but going to Russia for talks a week later. Several members of Congress and foreign diplomats expressed concern at the decision.

On Tuesday, State Department acting spokesman Mark Toner told reporters that the meeting's dates didn't fit in Tillerson's schedule.

Toner said the agency had sent "alternative dates" for the meeting and was "certainly appreciative of the effort to accommodate Secretary Tillerson."

"We are currently planning to hold the meeting of NATO foreign ministers on 31 March," a NATO official said. "Consultations on scheduling among allies are ongoing."

Read More