By Oliver Holmes
BEIRUT (Reuters) - Members of the Syrian opposition said on Tuesday that they had given up hope that the United States would deliver promised military aid to rebels as war planes and artillery smashed the central city of Homs.
U.S. congressional committees are holding up the plan to send weapons because of fears that such deliveries will not be decisive and that arms might end up in the hands of Islamist militants, U.S. national security sources said.
Both Democrats and Republicans on the committees worry that weapons could reach factions like the Nusra Front, which is one of the most effective rebel groups but has also been labeled by the United States as a front for al Qaeda in Iraq.
"The U.S. will not supply the weapons," said Mohammed Fizo, a rebel fighter. "They come up with excuses for why they are not with the Syrian revolution; because it's not unified, or that there are terrorists. But what is important is that they are not helping us."
Yasser, a 42-year-old nutritionist and opposition member who lives in Damascus, said indecision from Washington showed the United States' true aim was to keep both President Bashar al-Assad and Islamist rebels busy inside Syria.
"It to the benefit of the U.S. that both sides here in Syria continue in a slow war of attrition," he said. "Both sides are preoccupied with each other and can't make mayhem elsewhere."
He said the United States was especially worried by the prospect of an all-out victory for rebel groups, which might allow members of the Nusra Front, a hard-line Islamist group, to attack neighboring Israel once they toppled Assad.
Omar al-Hariri, an activist from Deraa where the uprising began during the Arab Spring two years ago, saw the further delay as tantamount to support for Assad, who has kept the Syrian-Israel border relatively quiet for decades.
"Israel is very concerned about who will replace Assad and whether or not they will be friendly to Israel's interests ... I am sure you are fully aware of how Israel is able to put pressure on the USA to hold onto Assad."
Rebels have pleaded with their international backers for weapons to battle Assad's forces. They say they have received shipments from Gulf countries and individual donors, but not enough to tackle Assad's national army and fighters from the powerful Lebanese militant movement Hezbollah, who are supporting him.
Many weapons used by the rebels appear to be made in China and Croatia.
The opposition Syrian National Coalition President, Ahmad Jarba, said he expected a weapons shipment from Saudi Arabia soon but that the rebels' military position was still weak.
This month Syrian forces have been targeting the central city of Homs, seen as crucial to the government's attempts to link the capital to Assad's coastal strongholds and divide rebel units in the north and south.
The Syrian Observatory for Human Rights, an anti-Assad Britain-based monitoring group, said central areas of Homs city were hit by air strikes, mortar bombs and tank rounds on Tuesday.
Al-Khalidiya, a northern district that links the outskirts of the city with the centre, was the focus of the violence and the 13th-century Khalid ibn al-Walid mosque, a prominent central landmark, had been hit. It also said the Krak de Chevaliers crusader castle, once a popular tourist site in Homs province, was the scene of clashes on Tuesday.
One hundred and forty km (90 miles) north of Damascus, Homs lies at a strategic crossing linking the capital with army bases in coastal regions controlled by Assad's Alawite sect, an offshoot of Shi'ite Islam that has dominated majority Sunni Syria since the 1960s.
The United Nations has expressed alarm at conditions in Homs, Syria's third largest city, saying last week that between 2,500 and 4,000 civilians were trapped there amid shortages of food, water, medicine, electricity and fuel.
The White House announced in June that it would arm vetted groups of Syrian rebels, after two years of avoiding involvement in the civil war which has killed more than 100,000 people.
Although the White House does not need specific congressional approval for the weapons plan, tacit rules observed by the executive branch on intelligence matters means President Barack Obama is unlikely to deliver weapons without the consent of congressional intelligence committees.
Committee members want to hear more about the administration's overall Syria policy, national security sources say, and about how arms deliveries will affect the battlefield.
Funding that the administration advised the congressional committees it wanted to use to pay for arms deliveries to Assad's opponents has been temporarily frozen, the sources said.
(Editing by Giles Elgood)