By Benjamin Kang Lim

HUAIROU, China, Sept 2 (Reuter) - A senior U.S. official warned on Saturday that heavy-handed Chinese security threatened the United Nations Fourth World Conference on Women in Beijing, and complained that he himself was being watched.

Timothy Wirth, Undersecretary of State for Global Affairs and a senior member of the U.S. delegation, called on U.N. Secretary-General Boutros Boutros-Ghali to take action to stop intrusive surveillance and restrictions on freedom of speech.

"The United Nations... has to demonstrate here that they can be firm and pull this off," Wirth said.

Anger at blanket Chinese security bubbled over at the Non Governmental Organisations (NGO) Forum on Women that overlaps with the U.N. meeting and is now taking place in the remote Beijing suburb of Huairou.

The U.N. conference opens on Monday.

On the fourth day of the NGO forum on Saturday, organisers gave Chinese officials 24 hours to ease up.

When the deadline expires, said conference committee member Salamo Fulivai, women delegates would be asked: "Say what do you want. Do you want to cancel? Do you want to boycott? Do you want to riot?."

"I cannot decide that from here," said Fulivai, Director Pacific of the Young Women's Christian Association (YWCA).

"We will go back to our constituencies to discuss appropriate action," said Irene Santiago, the forum's Filipino Executive Director, after meeting Chinese officials earlier in the day to press the women's complaints.

Controversy has surrounded the NGO forum since April when Chinese authorities panicked at the idea of radical feminists, including lesbians and human rights activists, roaming free in central Beijing and shifted the site to Huairou.

Their refusal to issue visas to scores of Tibetan women exiles fuelled more bitterness.

Once at the conference site, now a muddy swamp as a result of summer downpours, delegates found themselves surrounded by a large number of plainclothes security agents carrying video cameras and walkie-talkies.

Human rights activists and journalists were shadowed most closely.

Beijing banned anti-Chinese demonstrations and said other kinds of protests must be held in approved areas.

The Earth Times, a U.N.-endorsed newspaper that provides daily coverage of U.N. meetings, is still waiting for approval to publish its first edition featuring a column by U.S. First Lady Hillary Clinton.

Chen Muhua, president of the All-China Women's Federation, the official Chinese hosts of the U.N. conference, defended the need for security at one of the largest meetings ever organised by the world body.

"To guarantee the smooth running of the conference and the NGO forum, we have taken the necessary security and protection measures," she told a news conference. "If there were no proper measures, there would be confusion and lack of order and the meeting could not be held."

"If people feel something is not convenient, and have a specific demand, we can discuss how to improve the situation."

Wirth said the issue of security would now become a major focus at the U.N. conference.

He said he himself was being blatantly watched and was aware of similar complaints from reporters.

"We are going to be in a situation where the United Nations is going to have to step up and be very, very firm with the host country and with the commitments that they have," he said.