Disagreements over the proposed reforms could add to instability in Yemen, which borders oil giant Saudi Arabia.

Yemen is already struggling to quell the resurgent Al-Qaeda in the Arabian Peninsula militant group while also trying to cement a truce with Shiite rebels to end a civil war in the north and to end a separatist rebellion in the south.

The Al-Qaeda wing claimed responsibility for last December's botched attempt to bomb a Detroit-bound aircraft and for two US-bound parcel bombs intercepted in Britain and Dubai in October.

President Barack Obama's top counterterrorism adviser on Dec. 17 said US-Yemen ties had been strained by a US desire for faster economic and political reforms, which Washington hopes would slow the recruitment of Yemenis by militants.

Yemen's ruling party General People's Congress said in October it would participate in a parliamentary election scheduled for April, dashing opposition hopes the government would delay the poll to allow time for talks on long-promised reforms to guarantee free and fair parliamentary elections.

Originally due in February 2009, the parliamentary vote was delayed once after the government agreed to carry out election reforms. The opposition has said reforms have not materialized and has accused the ruling party of acting unilaterally.

According to local news reports, Yemen plans to hold a parliamentary vote on Saturday on proposed constitutional changes that would eliminate the term limit of two consecutive terms for the president, the State Department said.

The presidential term would be cut to five years from seven while women would get 44 more seats in parliament by raising the overall number of seats to 345 from 301 at present, the Yemen Post and Yemen Observer reported on their websites.

A Yemeni diplomat said he could not confirm the details in the press reports, saying that the government's full proposal would be put forward to the parliament on Saturday.

The diplomat, who spoke on condition of anonymity, said it was not clear when the parliament might vote on the proposals and he said they would then be put to a public vote during the parliamentary elections.

The US State Department made clear that it wanted action put off to allow for more dialogue with the opposition.

"The United States has seen reports regarding the apparent decision by Yemen's ruling General People's Conference to vote on a package of Constitutional reforms at a parliamentary session on Saturday, January 1," State Department spokesman Mark Toner said in a statement without naming the reports.

"We urgently call on all parties to delay parliamentary action and to return to the negotiating table to reach an agreement that will be welcomed by the Yemeni people as well as Yemen's friends," he added.

Mohammed Al-Basha, a spokesmen for the Yemeni embassy in Washington, said there was still time to work out an agreement and said the government's efforts to reach a deal had been hampered by differences among the many opposition parties.

"President Saleh continues to call for an open national dialogue," he said in a statement. "Coalition-building efforts (have) faced continuous hurdles and obstacles because of divisions amongst the opposition bloc. But there is still a window of opportunity to reach a reconciliation."