Former President Olusegun Obasanjo had agreed to cede the territory, which has offshore oil deposits, in line with a 2002 ruling by the International Court of Justice. The neighbours had argued about Bakassi for decades and come close to war over it.

After the deal, all seemed well until suspected Nigerian rebels killed 21 Cameroonian soldiers in Bakassi on November 12 in an unexplained raid and the Nigerian Senate said on November 22 the deal had not been ratified by parliament and thus was illegal.

The two events caused a flurry of diplomatic efforts to avert a flare up of tension with Cameroon.

In a letter read out to the Senate on Tuesday, Yar'Adua said his predecessor had duly sent the agreement to parliament at the time but it had never been ratified.

"I am again forwarding the agreement ... to you for ratification," he said.

Nigeria held general elections in April this year, so the president and the Senate have both changed since the Bakassi deal was signed. The letter did not say why the old Senate had not ratified the text.

The government had played down the importance of the new Senate's resolution and said the Bakassi deal was not in doubt. The phrasing of Yar'Adua's letter suggested he expected the Senate to rubber-stamp the agreement.

"You may kindly note that having subscribed to the jurisdiction of the International Court of Justice, Nigeria became duty bound to respect its judgment ... which confers sovereignty over the Bakassi peninsula to Cameroon," he wrote.

Since Obasanjo signed the agreement with his Cameroonian counterpart, Paul Biya, Nigerian troops have gradually handed over control of the territory to Cameroonians and the process is supposed to be complete by the end of next year.

Cameroonian and Nigerian officials met in the United States last Friday with U.N. mediators including Secretary-General Ban Ki-moon to discuss the situation in Bakassi.

U.N. officials said after the meeting they had been reassured that despite the Senate resolution Nigeria continued to be committed to the agreement.

The senators had not said whether their resolution was in any way connected to the unexplained attack on November 12.

Cameroon said 21 of its gendarmes were killed in the raid. The Nigerian army and government said they had nothing to do with it and relations with Cameroon were excellent.