The negotiations aim to allow more US troops, ships, aircraft and other equipment to pass through the Philippines, which had hosted tens of thousands of US troops until 1992.
"For the Americans, they typically have agreements like these that have a duration of 20 years. Right now, the Philippine delegation is looking at a much shorter duration," negotiator Carlos Sorreta, a Philippine assistant foreign secretary, said in statement.
Asked by AFP today to confirm if the US negotiators had proposed a 20-year agreement with Manila, American embassy spokesman Kurt Hoyer declined to comment.
Sorreta did not answer his phone when contacted by AFP.
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The Philippines earlier said the proposed framework had been tabled by the United States as the talks began in Manila in mid-August.
Specific time frames were absent in the agreed minutes of the August 29 meeting in Washington, a copy of which the Philippine foreign department released to the press today with Sorreta's statement.
It said the US would host the next round of talks in the second week of September.
Philippine officials have said an increased US presence was part of Manila's efforts to build a credible defence posture as it faces territorial disputes at sea with China.
Manila accuses China of aggressively pushing its territorial claims over most of the South China Sea, including waters close to Philippine shores.
The United States, meanwhile, wants arrangements similar to what it has with Australia and Singapore as it seeks to bolster its ties across Southeast Asia, partly to counter China's growing military power.
The United States once held Clark Air Base and Subic Naval Base, both near Manila, but was forced to hand them back in 1992 amid growing anti-US sentiment and a rental dispute.
A new accord in 1999 allowed troops to return to the Philippines for joint military exercises every year.
Several hundred US Special Forces troops are also on short-term assignments at Philippine bases in the south, where they train and advise local troops fighting Islamic militants.