Senate Democrats on Tuesday sent a letter to Republican leaders urging them to drop their efforts to repeal and replace Obamacare and instead to work with them on drafting fixes to the healthcare law.

"We write to request that the Senate work in a bipartisan, open and transparent way to improve and reform the healthcare system," they wrote in the letter, signed by all 58 members. "Democrats stand ready – as we always have – to develop legislation with Republicans that will improve quality, lower costs and expand coverage for all Americans. But Republicans need to set aside their current partisan efforts and work with us to get this done."

Republicans have aimed to advance their repeal efforts through a measure known as reconciliation, which requires only a simple majority in the Senate for passage instead of the 60 votes typically needed to break a filibuster. Because Republicans have a slim, 52-person majority in the upper chamber, they cannot afford to lose more than two votes to pass a healthcare bill, assuming a tie-breaking vote by Vice President Mike Pence. Several Republican senators have said they are opposed to aspects of the House bill, the American Health Care Act, because it would cut spending on Medicaid, defund Planned Parenthood for a year and increase costs for older, low-income adults, as well as increase the number of uninsured by 24 million by 2026. Several lawmakers also have expressed concerns that people with pre-existing illnesses would not be adequately safeguarded.

The call for bipartisanship isn't coming only from Democrats. Republican Sen. Bill Cassidy of Louisiana has also called for Democrats to join him in the debate on healthcare. He and Sen. Susan Collins, a centrist Republican from Maine, have introduced a bill that would allow states to keep Obamacare or draft their own plan. Neither Cassidy nor Collins, however, has been included in the GOP's Senate working group that is working to draft a bill to repeal and replace Obamacare.

In their letter, Democrats said they wanted to work on legislation that would address reducing the cost of prescription drugs, reducing medical costs for consumers, stabilizing the Obamacare exchanges, covering more people and making it easier for small businesses to offer coverage.

"If repeal is abandoned, we stand ready to work with you to help all Americans get the affordable healthcare they need," Democrats wrote. "Instead of trying to change the House's 'repeal and replace' legislation, which has an uncertain path to the president's desk, you could instead choose to work with us on a bipartisan health reform package that can garner 60 votes in the Senate and pass the House with Republican and Democratic votes."

Democrats also have been waging battles to protect Obamacare by attacking various portions of the American Health Care Act. Earlier Tuesday, several Senate Democrats said during a press conference that Republicans are taking away veterans' access to tax credits to get healthcare on the individual market, which is used by people who don't have insurance through work or through the government.

A quartet of Democrats said that the version of the American Health Care Act that narrowly passed the House last week doesn't contain a fix that allows veterans to get the tax credits if they seek healthcare outside of a Veterans Affairs hospital. An earlier version of the AHCA did include the fix, but it was taken out because of concerns the bill wouldn't pass the Senate's budget rules under reconciliation. Sen. Tammy Duckworth, D-Ill., a veteran herself, said the omission was no mistake."It was never an oversight or an accident," she said at a press conference Tuesday. "Why would they have the language to protect veterans specifically and then say they took it out in the technical amendment?"