In a speech to parliament he revealed that Malaysia's Prime Minister Mahathir Mohamad response to Singapore's proposals showed that differences remained.

Singapore had not set a deadline but there was a sense of urgency "to resolve these issues as soon as possible," he said.

The city-state has already extended the deadline for a Malaysia-owned railway station in the heart of the republic to be moved.

Other issues include an agreement on the long-term water supply to Singapore, the use by the Singapore's air force of Malaysian air space, and the location of Malaysia's Customs, Immigration and Quarantine facilities.

Malaysia also wants Singapore to allow Malaysians who worked in the republic to withdraw money from their pension fund before retirement age.

Jayakumar said the letter from Mahathir was only received a week ago and a "preliminary study shows that there are variations on some points" between Mahathir's reply and Senior Minister Lee Kuan Yew's understanding with the Malaysian leader during talks last August.

"At first blush, the differences do not appear that great," Jayakumar said.

Singapore is reliant on Malaysia for much of its water needs, and the minister said officials needed to study Malaysia's proposed price for water under a new agreement from 2011 to 2061, and for the period after 2061 when the Johor River Water Agreement ends.

"Having said that, let me stress that apart from the supply of water there are also other outstanding items that need to be settled at the same time."

Singapore had agreed in principle to Malaysia's request to move its railway station to Kranji on the northern border with Malaysia on the condition that all outstanding issues were settled as a package.