UNITED NATIONS (Reuters) - Syria urged the United Nations on Tuesday to send scientists to investigate its claim of a chemical attack by rebels in Aleppo, but said it does not trust accusations by the United States, Britain and others that such weapons were used elsewhere in the country.
Syria's U.N. Ambassador Bashar Ja'afari also accused "armed terrorist groups" of spreading powder from plastic bags - which he described as "probably a kind of chemical material" - among crowds in the northern city of Saraqeb on Monday.
"Many people were affected by this heinous, irresponsible act and the wounded, as well as the victims, had manifested signs similar to those during the use of chemical weapons," Ja'afari told a news conference at the United Nations in New York.
Opposition groups have accused the government of the attack. Ja'afari alleged that the rebels had "prearranged" for the victims to be transported into neighbouring Turkey so proof of a chemical attack could be gathered and blamed on the government.
U.S. President Barack Obama on Tuesday said that there was evidence that chemical weapons had been used during Syria's two year conflict, but that it was not yet known how the chemical weapons were used, when they were used and who used them.
The United States and Syria both believe a credible U.N. investigation is the best way to establish chemical weapons use. But nearly six weeks after Syria initially asked for such an inquiry, investigators have been unable to enter the country.
The Syrian government and the opposition blame each other for alleged chemical weapons attacks in Aleppo in March and Homs in December. Syria wants the U.N. team to probe only the Aleppo attack, but Ban wants the inquiry to cover both incidents.
"Let us now fulfil, achieve in a credible manner, impartial, independent manner, the investigation (in Aleppo)," Ja'afari said. "Then if the Syrian government, and the (U.N.) secretary-general and the Security Council members feel that these (other) allegations are also credible, the Syrian government might examine the possibility of asking for further investigation."
Ja'afari said Syria and the United Nations have so far exchanged 17 letters on the issue of access for investigators.
Obama has warned Syria's government that the use of chemical weapons could trigger unspecified consequences. He told a news conference on Tuesday that he had asked the U.S. military to prepare options on Syria, but declined to give further details.
The United States and Britain said last week they had limited but growing evidence that chemical weapons, possibly the nerve agent sarin, had been used during Syria's civil war in which more than 70,000 people have been killed.
"We have a problem with trust with those who are providing these so called allegations ... because they are involved in supporting the terrorist groups and the armed groups in Syria," Ja'afari said. The United States and Britain said they have provided non-lethal support to armed opposition groups in Syria.
He said Syria had not been given evidence of the Western claims of chemical attacks.
U.N. Secretary-General Ban Ki-moon said on Monday that while waiting to gain access to Syria, the U.N. investigators were gathering and analyzing available information on the alleged attacks, which included possible visits to countries that said they had evidence of chemical weapons use.
"The Syrian government believes that the only way for the investigation ... to check the truth of what happened is through going to Syria and conducting investigations on the ground ... and not touring capitals here and there," Ja'afari said.
The Organisation for the Prohibition of Chemical Weapons, which works on U.N. inquiries, has said assertions of chemical weapon use by Western and Israeli officials citing photos, sporadic shelling and traces of toxins do not meet the standard of proof needed for U.N. investigators.
(Reporting by Michelle Nichols; editing by Jackie Frank)