The Philippines Vice-President, Teofisto Guingona, has stepped down from his post as foreign minister, the presidential palace has said.

President Gloria Arroyo has accepted his resignation, a statement said, referring to "honest differences of opinion".

Mr Guingona appeared shocked by the news

Mrs Arroyo said in her acceptance letter that she would like Mr Guingona to continue in his post as vice-president.

But Mr Guingona, 73, told reporters he had not resigned from the foreign office and was seeking clarification from the palace.

Mr Guingona has objected to the presence of US troops in the country, who are training Philippines troops to combat Islamic rebels in the country's south.

Clash over troops

"You are relinquishing the position of Secretary of Foreign Affairs," Mrs Arroyo said in a letter to Mr Guingona which was released to the press on Thursday.

Mrs Arroyo gave no official reason for Mr Guingona's resignation, although her letter referred to "honest differences of opinion that tend to divide".

I did not resign, period

Philippines Vice President Teofisto Guingona

Mrs Arroyo, who appointed Mr Guingona to vice-president and foreign minister when she took office last January, had initially persuaded him to support her decision to bring in the US military.

"You have done a good job," Mrs Arroyo said in her letter.

"When you brought to me your reservations about Balikatan (joint US-Philippines military exercises) in Basilan, I asked you to help craft the terms of reference."

She said in the letter she wanted Mr Guingona to instead accept a role as an adviser for foreign affairs.

Conflicting reports

But minutes after a presidential aide released the letter, Mr Guingona told reporters: "I did not resign, period."

He is then reported to have stormed back into the foreign affairs office.

He said he had called Mrs Arroyo's executive secretary, Alberto Romulo, to ask him to clarify the announcement.

The government's chief spokesman, Silvestre Afable, said that although Mr Guingona had not submitted a written resignation, the issue "was discussed between them".

Mr Afable said Mrs Arroyo wrote the acceptance letter following her meeting with Mr Guingona, adding that "the letter of the president stands".

Staff at Mr Guingona's office said they had only heard about the resignation from the media.

In recent days Mrs Arroyo has publicly supported calls for fresh military exercises between the Philippines and the US.

The six-month training exercises are due to end next month.

Analysts say the alleged dispute between Mrs Arroyo and Mr Guingona comes amid a backdrop of declining popularity for the president.