NEW DELHI: The Congress on Wednesday expressed disappointment over the resignation of Nitish Kumar as Bihar chief minister and said it will continue to strive to resolve the differences in the 'grand alliance'.

Congress chief spokesperson Randeep Surjewala said the 'grand alliance' was given a mandate for five years and the Congress will strive to respect that.

"We are deeply disappointed by the news of resignation of Bihar chief minister Nitish Kumar. We, in the Congress party, particularly Congress president and party vice president have great respect and affection for Nitish Kumar," he said.

The Congress leader said the 'Mahagathbandhan' was given a five-year mandate by people of Bihar based on the policies, principles and cumulative leadership that was presented.

It was also a mandate against the BJP and Prime Minister Narender Modi, who challenged the honour of Bihar, he said.

"Responsibility lies up on each one of us to respect this mandate. The Congress party will do everything within its means (to see to it) that this mandate is honoured," he said.

"Any differences of opinion that may have cropped up we will try and sort them out by speaking to each other in an amicable and cordial fashion," he said.

Nitish Kumar threw a political bombshell by announcing his resignation, citing irreconcilable differences with ally RJD on the issue of corruption charges against his deputy Tejashwi Yadav.

"In the circumstances that prevail in Bihar, it became difficult to run the grand alliance government," Kumar told reporters outside Raj Bhavan in Patna after submitting his resignation to Governor Keshri Nath Tripathi.